Develop Reference

How to count occurrence of Polish characters in .txt file

I have to prepare a .txt file and count how many times each character of alphabet occurs in the file. I've found a very nice piece of code, but unfortunately, it doesn't work with Polish characters like ą,ę,ć,ó,ż,ź. Even though I put them in the array, for some reason they are not found in the .txt file so the output is 0.
Does anyone know why? Maybe I should count them differently, with "Switch" or something similar.
Before anyone asks - yes, the .txt file is saved with UTF-8 :)
public static void main(String[] args) throws FileNotFoundException {
int ch;
BufferedReader reader;
try {
int counter = 0;
for (char a : "AĄĆĘÓBCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray()) {
reader = new BufferedReader(new FileReader("C:\\Users\\User\\Desktop\\pan.txt"));
char toSearch = a;
counter = 0;
try {
while ((ch = reader.read()) != -1) {
if (a == Character.toUpperCase((char) ch)) {
counter++;
}
}
} catch (IOException e) {
System.out.println("Error");
e.printStackTrace();
}
System.out.println(toSearch + " occurs " + counter);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}

Looks like your problem related to encoding and default system charset
try to change reader variable to this
InputStreamReader reader = new InputStreamReader(new FileInputStream("C:\\Users\\User\\Desktop\\pan.txt"), "UTF-8");

try this:
I suggest that you use NIO and this code I have written for you using NIO, RandomAccessFile and MappedByteBuffer that is faster:
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.util.HashMap;
import java.util.Map;
public class FileReadNio
{
public static void main(String[] args) throws IOException
{
Map<Character, Integer> charCountMap = new HashMap<>();
RandomAccessFile rndFile = new RandomAccessFile
("c:\\test123.txt", "r");
FileChannel inChannel = rndFile.getChannel();
MappedByteBuffer buffer = inChannel.map(FileChannel.MapMode.READ_ONLY, 0, inChannel.size());
buffer.load();
for (int i = 0; i < buffer.limit(); i++)
{
char c = (char) buffer.get();
if (charCountMap.get(c) != null) {
int cnt = charCountMap.get(c);
charCountMap.put(c, ++cnt);
}
else
{
charCountMap.put(c, 1);
}
}
for (Map.Entry<Character,Integer> characterIntegerEntry : charCountMap.entrySet()) {
System.out.printf("char: %s :: count=%d", characterIntegerEntry.getKey(), characterIntegerEntry.getValue());
System.out.println();
}
buffer.clear();
inChannel.close();
rndFile.close();
}
}

The text file becomes empty when I try to overwrite it, and its content gets recovered when I restart the OS [duplicate]

How do I replace a line of text found within a text file?
I have a string such as:
Do the dishes0
And I want to update it with:
Do the dishes1
(and vise versa)
How do I accomplish this?
ActionListener al = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
JCheckBox checkbox = (JCheckBox) e.getSource();
if (checkbox.isSelected()) {
System.out.println("Selected");
String s = checkbox.getText();
replaceSelected(s, "1");
} else {
System.out.println("Deselected");
String s = checkbox.getText();
replaceSelected(s, "0");
}
}
};
public static void replaceSelected(String replaceWith, String type) {
}
By the way, I want to replace ONLY the line that was read. NOT the entire file.

At the bottom, I have a general solution to replace lines in a file. But first, here is the answer to the specific question at hand. Helper function:
public static void replaceSelected(String replaceWith, String type) {
try {
// input the file content to the StringBuffer "input"
BufferedReader file = new BufferedReader(new FileReader("notes.txt"));
StringBuffer inputBuffer = new StringBuffer();
String line;
while ((line = file.readLine()) != null) {
inputBuffer.append(line);
inputBuffer.append('\n');
}
file.close();
String inputStr = inputBuffer.toString();
System.out.println(inputStr); // display the original file for debugging
// logic to replace lines in the string (could use regex here to be generic)
if (type.equals("0")) {
inputStr = inputStr.replace(replaceWith + "1", replaceWith + "0");
} else if (type.equals("1")) {
inputStr = inputStr.replace(replaceWith + "0", replaceWith + "1");
}
// display the new file for debugging
System.out.println("----------------------------------\n" + inputStr);
// write the new string with the replaced line OVER the same file
FileOutputStream fileOut = new FileOutputStream("notes.txt");
fileOut.write(inputStr.getBytes());
fileOut.close();
} catch (Exception e) {
System.out.println("Problem reading file.");
}
}
Then call it:
public static void main(String[] args) {
replaceSelected("Do the dishes", "1");
}
Original Text File Content:
Do the dishes0
Feed the dog0
Cleaned my room1
Output:
Do the dishes0
Feed the dog0
Cleaned my room1
----------------------------------
Do the dishes1
Feed the dog0
Cleaned my room1
New text file content:
Do the dishes1
Feed the dog0
Cleaned my room1
And as a note, if the text file was:
Do the dishes1
Feed the dog0
Cleaned my room1
and you used the method replaceSelected("Do the dishes", "1");,
it would just not change the file.
Since this question is pretty specific, I'll add a more general solution here for future readers (based on the title).
// read file one line at a time
// replace line as you read the file and store updated lines in StringBuffer
// overwrite the file with the new lines
public static void replaceLines() {
try {
// input the (modified) file content to the StringBuffer "input"
BufferedReader file = new BufferedReader(new FileReader("notes.txt"));
StringBuffer inputBuffer = new StringBuffer();
String line;
while ((line = file.readLine()) != null) {
line = ... // replace the line here
inputBuffer.append(line);
inputBuffer.append('\n');
}
file.close();
// write the new string with the replaced line OVER the same file
FileOutputStream fileOut = new FileOutputStream("notes.txt");
fileOut.write(inputBuffer.toString().getBytes());
fileOut.close();
} catch (Exception e) {
System.out.println("Problem reading file.");
}
}

Since Java 7 this is very easy and intuitive to do.
List<String> fileContent = new ArrayList<>(Files.readAllLines(FILE_PATH, StandardCharsets.UTF_8));
for (int i = 0; i < fileContent.size(); i++) {
if (fileContent.get(i).equals("old line")) {
fileContent.set(i, "new line");
break;
}
}
Files.write(FILE_PATH, fileContent, StandardCharsets.UTF_8);
Basically you read the whole file to a List, edit the list and finally write the list back to file.
FILE_PATH represents the Path of the file.

If replacement is of different length:
Read file until you find the string you want to replace.
Read into memory the part after text you want to replace, all of it.
Truncate the file at start of the part you want to replace.
Write replacement.
Write rest of the file from step 2.
If replacement is of same length:
Read file until you find the string you want to replace.
Set file position to start of the part you want to replace.
Write replacement, overwriting part of file.
This is the best you can get, with constraints of your question. However, at least the example in question is replacing string of same length, So the second way should work.
Also be aware: Java strings are Unicode text, while text files are bytes with some encoding. If encoding is UTF8, and your text is not Latin1 (or plain 7-bit ASCII), you have to check length of encoded byte array, not length of Java string.

I was going to answer this question. Then I saw it get marked as a duplicate of this question, after I'd written the code, so I am going to post my solution here.
Keeping in mind that you have to re-write the text file. First I read the entire file, and store it in a string. Then I store each line as a index of a string array, ex line one = array index 0. I then edit the index corresponding to the line that you wish to edit. Once this is done I concatenate all the strings in the array into a single string. Then I write the new string into the file, which writes over the old content. Don't worry about losing your old content as it has been written again with the edit. below is the code I used.
public class App {
public static void main(String[] args) {
String file = "file.txt";
String newLineContent = "Hello my name is bob";
int lineToBeEdited = 3;
ChangeLineInFile changeFile = new ChangeLineInFile();
changeFile.changeALineInATextFile(file, newLineContent, lineToBeEdited);
}
}
And the class.
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
public class ChangeLineInFile {
public void changeALineInATextFile(String fileName, String newLine, int lineNumber) {
String content = new String();
String editedContent = new String();
content = readFile(fileName);
editedContent = editLineInContent(content, newLine, lineNumber);
writeToFile(fileName, editedContent);
}
private static int numberOfLinesInFile(String content) {
int numberOfLines = 0;
int index = 0;
int lastIndex = 0;
lastIndex = content.length() - 1;
while (true) {
if (content.charAt(index) == '\n') {
numberOfLines++;
}
if (index == lastIndex) {
numberOfLines = numberOfLines + 1;
break;
}
index++;
}
return numberOfLines;
}
private static String[] turnFileIntoArrayOfStrings(String content, int lines) {
String[] array = new String[lines];
int index = 0;
int tempInt = 0;
int startIndext = 0;
int lastIndex = content.length() - 1;
while (true) {
if (content.charAt(index) == '\n') {
tempInt++;
String temp2 = new String();
for (int i = 0; i < index - startIndext; i++) {
temp2 += content.charAt(startIndext + i);
}
startIndext = index;
array[tempInt - 1] = temp2;
}
if (index == lastIndex) {
tempInt++;
String temp2 = new String();
for (int i = 0; i < index - startIndext + 1; i++) {
temp2 += content.charAt(startIndext + i);
}
array[tempInt - 1] = temp2;
break;
}
index++;
}
return array;
}
private static String editLineInContent(String content, String newLine, int line) {
int lineNumber = 0;
lineNumber = numberOfLinesInFile(content);
String[] lines = new String[lineNumber];
lines = turnFileIntoArrayOfStrings(content, lineNumber);
if (line != 1) {
lines[line - 1] = "\n" + newLine;
} else {
lines[line - 1] = newLine;
}
content = new String();
for (int i = 0; i < lineNumber; i++) {
content += lines[i];
}
return content;
}
private static void writeToFile(String file, String content) {
try (Writer writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), "utf-8"))) {
writer.write(content);
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private static String readFile(String filename) {
String content = null;
File file = new File(filename);
FileReader reader = null;
try {
reader = new FileReader(file);
char[] chars = new char[(int) file.length()];
reader.read(chars);
content = new String(chars);
reader.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (reader != null) {
try {
reader.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
return content;
}
}

Sharing the experience with Java Util Stream
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public static void replaceLine(String filePath, String originalLineText, String newLineText) {
Path path = Paths.get(filePath);
// Get all the lines
try (Stream<String> stream = Files.lines(path, StandardCharsets.UTF_8)) {
// Do the line replace
List<String> list = stream.map(line -> line.equals(originalLineText) ? newLineText : line)
.collect(Collectors.toList());
// Write the content back
Files.write(path, list, StandardCharsets.UTF_8);
} catch (IOException e) {
LOG.error("IOException for : " + path, e);
e.printStackTrace();
}
}
Usage
replaceLine("test.txt", "Do the dishes0", "Do the dishes1");

//Read the file data
BufferedReader file = new BufferedReader(new FileReader(filepath));
StringBuffer inputBuffer = new StringBuffer();
String line;
while ((line = file.readLine()) != null) {
inputBuffer.append(line);
inputBuffer.append('\n');
}
file.close();
String inputStr = inputBuffer.toString();
// logic to replace lines in the string (could use regex here to be generic)
inputStr = inputStr.replace(str, " ");
//'str' is the string need to update in this case it is updating with nothing
// write the new string with the replaced line OVER the same file
FileOutputStream fileOut = new FileOutputStream(filer);
fileOut.write(inputStr.getBytes());
fileOut.close();

Well you would need to get a file with JFileChooser and then read through the lines of the file using a scanner and the hasNext() function
http://docs.oracle.com/javase/7/docs/api/javax/swing/JFileChooser.html
once you do that you can save the line into a variable and manipulate the contents.

just how to replace strings :) as i do
first arg will be filename second target string third one the string to be replaced instead of targe
public class ReplaceString{
public static void main(String[] args)throws Exception {
if(args.length<3)System.exit(0);
String targetStr = args[1];
String altStr = args[2];
java.io.File file = new java.io.File(args[0]);
java.util.Scanner scanner = new java.util.Scanner(file);
StringBuilder buffer = new StringBuilder();
while(scanner.hasNext()){
buffer.append(scanner.nextLine().replaceAll(targetStr, altStr));
if(scanner.hasNext())buffer.append("\n");
}
scanner.close();
java.io.PrintWriter printer = new java.io.PrintWriter(file);
printer.print(buffer);
printer.close();
}
}

Is there any compression method in java to reduce the number of charaters in a string?

I am currently facing a problem while compressing a string to fewer characters in java.
I have a huge string which is about 751396 characters and there is a requirement of compressing the string into a 1500 characters.
I have tried GZIP Compressor, Inflater & Deflater but these libraries return byte arrays
Then I tried LZ-String compressor in which I was able to get satisfactory results using UTF16 encoding and base64 encoding, But these compression return some characters which are neither alphanumeric nor are they included in the symbols list provided.
N.B. The list for the Symbols is [+,-,*,/,!,#,#]
is there any other technique of compressing the string into another string with fewer characters and providing at least 30% of compression ratio.
The codes which I am using for GZip compression is as follows:-
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;
public class GZIPCompression {
public static byte[] compress(final String str) throws IOException {
if ((str == null) || (str.length() == 0)) {
return null;
}
ByteArrayOutputStream obj = new ByteArrayOutputStream();
GZIPOutputStream gzip = new GZIPOutputStream(obj);
gzip.write(str.getBytes("UTF-8"));
gzip.close();
return obj.toByteArray();
}
public static String decompress(final byte[] compressed) throws IOException {
String outStr = "";
if ((compressed == null) || (compressed.length == 0)) {
return "";
}
if (isCompressed(compressed)) {
GZIPInputStream gis = new GZIPInputStream(new ByteArrayInputStream(compressed));
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(gis, "UTF-8"));
String line;
while ((line = bufferedReader.readLine()) != null) {
outStr += line;
}
} else {
outStr = new String(compressed);
}
return outStr;
}
public static boolean isCompressed(final byte[] compressed) {
return (compressed[0] == (byte) (GZIPInputStream.GZIP_MAGIC)) && (compressed[1] == (byte) (GZIPInputStream.GZIP_MAGIC >> 8));
}
}
The code for the Inflater & Deflater program is as follows:-
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Arrays;
import java.util.zip.DataFormatException;
import java.util.zip.Deflater;
import java.util.zip.Inflater;
public class Apple {
public static void main(String[] args) {
String sr = " [120,-100,-19,89,91,79,-21,56,16,-2,43,40,-49,104,55,113,-18,-68,-91,-23,21,104,90,-38,-62,10,-83,120,48,-83,91,34,-46,-92,-21,-92,8,-124,-8,-17,103,-100,-92,77,-22,-38,-25,112,86,27,-119,106,65,84,-86,103,-58,-10,124,-98,-15,101,-66,-66,43,25,126,-99,-112,116,-109,-60,41,81,46,-34,-107,-57,36,121,14,-29,-43,-20,109,3,77,101,-94,-100,43,120,-79,-115,50,63,-39,-58,25,8,52,16,-52,-97,-62,104,-79,19,-88,32,8,-29,37,-114,-77,-70,-92,71,-78,89,125,-36,-65,-33,-107,5,-50,-40,-120,-86,-11,39,82,-31,95,-77,-40,-48,-21,-94,15,82,13,11,-58,-115,112,-102,-6,-55,-126,-103,-7,126,-65,53,-22,-113,-64,-58,123,-63,97,52,37,-85,53,97,-106,-17,74,55,10,87,79,-39,96,-63,-100,65,76,31,-46,40,-116,73,-39,111,-38,3,81,97,18,108,-41,-113,-124,-126,-52,-48,-100,-62,-50,-89,120,-103,-107,-56,108,-99,9,71,52,92,-123,49,52,91,-41,-109,125,19,44,55,9,-51,102,-124,-82,-61,24,71,-96,5,85,-101,-92,25,-76,-78,48,-55,-51,71,-61,67,-103,-92,-49,6,-45,108,75,73,27,-80,-49,-62,53,-101,23,-64,-25,75,-96,89,103,72,-67,48,-44,11,-107,-83,-105,71,105,-8,-126,35,-119,29,-70,-48,74,-69,-10,-106,-18,92,-48,-98,104,122,-90,-85,48,93,10,-118,2,108,-78,-100,102,-55,38,85,46,-44,115,-27,46,-60,-123,23,-2,-106,82,18,-49,-33,-54,21,26,4,-109,-35,-86,-114,-15,107,23,-125,119,36,-125,70,-102,71,-55,23,-58,96,47,5,-60,-13,-61,-24,-80,-28,96,97,105,-31,52,-100,123,101,60,53,-61,112,33,12,48,54,19,-61,-56,74,-112,116,41,-127,-42,74,41,-28,-69,-4,34,-53,109,-68,-64,-113,17,1,-7,-3,77,-18,-8,44,-55,112,4,-39,-77,27,12,68,61,-102,-92,-23,126,112,-45,48,-64,-91,100,-67,14,-45,-76,88,11,-45,-2,-61,-75,-108,-113,-113,-13,67,0,-99,-114,12,64,-91,17,3,-128,-124,108,14,0,-46,28,-99,3,-32,104,66,0,-35,-82,12,64,-91,-111,0,48,-35,6,1,-40,-74,-54,1,-48,84,93,-120,-96,-33,-105,33,-88,52,98,4,-70,-34,96,8,116,-45,114,121,4,-70,24,-63,-27,-91,12,65,-91,-111,32,112,27,-116,-127,-127,44,-115,71,96,-70,66,4,87,87,50,4,-107,70,-116,-64,112,26,-116,-127,-87,89,54,-113,-64,21,-57,-32,-6,90,-122,-96,-46,-120,17,-104,77,34,-80,-112,-50,111,100,36,-55,-94,-31,80,-122,-96,-46,-120,17,-40,77,30,69,-74,-87,-15,89,-124,36,103,81,16,-56,16,84,26,49,2,71,111,112,31,56,-82,-55,-97,69,-70,110,10,17,-116,70,50,4,-107,70,-116,-64,117,26,68,-96,-87,-90,-31,-16,16,92,49,-124,-101,27,25,-124,74,35,-71,-110,-31,-38,108,16,3,-46,85,126,51,27,-106,56,-111,38,19,25,-122,74,35,-63,-48,-24,-99,-96,25,8,-103,-4,-61,66,-78,-99,-89,83,25,-122,74,35,-63,96,-94,38,115,-55,-46,85,-2,72,-78,52,113,28,102,51,25,-122,74,35,-63,96,55,-71,-93,53,-57,52,-8,45,109,-19,-10,-61,-61,-57,-71,-78,43,43,-90,25,-50,-74,48,57,-100,96,-73,41,-95,51,-118,-25,-49,121,93,48,25,-34,-113,6,-82,-83,-62,-3,91,124,116,-37,-123,67,-56,50,12,3,-23,-102,-19,-72,-106,-125,92,56,-25,-64,39,-16,99,-76,-51,54,-37,18,-28,106,-123,87,-60,-117,23,67,-126,-93,-76,27,1,-100,-36,-29,-68,-108,41,-86,-118,-78,18,41,94,-53,71,-75,8,91,46,-80,-50,-21,20,-74,58,-108,-32,-25,-37,-51,-2,-127,93,-82,-93,-16,69,46,20,10,94,-43,-99,127,-74,-84,84,0,31,-40,12,59,41,76,90,127,-58,-77,64,-46,112,83,-106,10,-29,105,-105,57,-73,-49,64,-107,-91,-62,-95,-55,109,-69,110,-94,-101,-24,-40,-92,55,-99,-43,76,28,-29,-40,-30,-22,-54,-81,15,-14,-15,112,28,108,-45,97,-50,82,28,-89,120,-50,122,117,9,-55,-105,120,74,-24,75,56,39,-2,19,-90,43,-112,56,-4,-117,51,47,16,-123,111,126,54,-53,-124,-64,-94,80,-78,-24,-122,36,90,-28,-21,-100,71,2,-60,53,-55,42,-65,-59,-64,-63,-63,98,76,-109,100,89,-74,-58,-112,-5,-84,116,-37,-105,-117,65,94,-65,-58,-117,-68,113,-49,-118,46,-88,-54,70,-53,86,72,-77,39,-82,79,-25,117,19,-46,-73,118,81,-39,-42,21,-125,52,-35,66,21,-99,-105,-60,-12,-83,84,6,121,-23,-122,-93,48,43,36,-112,-54,62,43,-91,-65,-66,-101,-125,-68,-64,111,-60,-49,-5,-1,-50,79,112,52,-33,-73,-5,-8,-105,45,-40,15,-20,91,-71,-79,-18,122,67,118,-78,49,-55,97,-10,6,-55,89,-47,-95,80,-18,-113,39,-106,-25,-121,-3,-81,-123,-3,107,-118,-86,80,50,-71,-34,99,-65,-27,11,123,-113,59,94,112,59,-101,-98,121,65,-5,-84,-43,-71,-13,38,94,-81,-61,-115,-90,25,-68,47,-63,-99,-60,-105,-102,66,-18,75,32,-13,37,-16,-4,-2,-24,55,93,-71,12,36,-82,92,122,-125,-32,108,-40,-15,120,127,116,-109,31,-94,-35,-110,12,-47,30,120,-83,-50,108,-32,127,110,24,95,6,-53,-9,-90,-3,-65,58,-97,89,-27,-121,-113,-4,-74,-84,81,86,-58,17,101,5,23,-54,33,101,85,-29,20,126,66,89,-63,-33,39,73,43,-3,-41,-92,85,-50,66,125,-98,-76,-54,57,-82,127,69,90,25,123,50,74,117,-10,100,-108,-128,-76,-86,-20,-64,72,64,90,33,70,90,53,-55,89,125,85,-54,7,-23,-4,-3,117,98,-108,-113,-125,-8,119,-27,-87,81,62,22,66,39,78,-7,-24,26,79,124,-98,26,-27,-125,-48,17,113,120,106,-108,-113,-61,111,-28,-109,-93,124,44,62,-117,78,-116,-14,113,-43,-93,26,-9,-28,40,31,75,-27,121,-73,19,-92,124,44,126,51,-97,32,-27,99,-13,-44,-37,9,82,62,38,127,36,-99,32,-27,-29,30,-47,86,95,-97,-14,41,-33,-14,-115,-110,62,-59,-77,-108,39,125,10,-23,79,73,-97,-39,-92,-50,-24,-120,56,-97,-33,-90,-123,12,83,-1,21,45,-92,33,1,115,116,-56,11,25,34,94,-56,-74,63,-59,11,-79,95,43,-72,119,-87,-50,-1,-112,-73,-69,-52,-66,-119,-95,-26,-35,-4,38,-122,-66,-119,-95,-1,27,49,4,-97,31,15,0,-88,84]";
byte[] data = sr.getBytes();
try {
String x = new String(decompress(compress(data)));
System.out.println("decompressed " + x);
} catch (IOException | DataFormatException e) {
e.printStackTrace();
}
}
public static byte[] compress(byte[] data) throws IOException {
Deflater deflater = new Deflater();
deflater.setInput(data);
ByteArrayOutputStream outputStream = new ByteArrayOutputStream(data.length);
deflater.finish();
byte[] buffer = new byte[1024];
while (!deflater.finished()) {
int count = deflater.deflate(buffer);
outputStream.write(buffer, 0, count);
}
outputStream.close();
byte[] output = outputStream.toByteArray();
System.out.println("Original: " + data.length);
System.out.println("Compressed: " + output.length);
return output;
}
public static byte[] decompress(byte[] data) throws IOException, DataFormatException {
Inflater inflater = new Inflater();
inflater.setInput(data);
ByteArrayOutputStream outputStream = new ByteArrayOutputStream(data.length);
byte[] buffer = new byte[1024];
while (!inflater.finished()) {
int count = inflater.inflate(buffer);
outputStream.write(buffer, 0, count);
}
outputStream.close();
byte[] output = outputStream.toByteArray();
System.out.println();
return output;
}
}
A sample of how the data will look like:-
"120,-100,-19,89,91,79,-21,56,16,-2,43,40,-49,104,55,113,-18,-68,-91,-23,21,104,90,-38,-62,10,-83,120,48,-83,91,34,-46,-92,-21,-92,8,-124,-8,-17,103,-100,-92,77,-22,-38,-25,112,86,27,-119,106,65,84,-86,103,-58,-10,124,-98,-15,101,-66,-66,43,25,126,-99,-112,116,-109,-60,41,81,46,-34,-107,-57,36,121,14,-29,-43,-20,109,3,77,101,-94,-100,43,120,-79,-115,50,63,-39,-58,25,8,52,16,-52,-97,-62,104,-79,19,-88,32,8,-29,37,-114,-77,-70,-92,71,-78,89,125,-36,-65,-33,-107,5,-50,-40,-120,-86,-11,39,82,-31,95,-77,-40,-48,-21,-94,15,82,13,11,-58,-115,112,-102,-6,-55,-126,-103,-7,126,-65,53,-22,-113,-64,-58,123,-63,97,52,37,-85,53,97,-106,-17,74,55,10,87,79,-39,96,-63,-100,65,76,31,-46,40,-116,73,-39,111,-38,3,81,97,18,108,-41,-113,-124,-126,-52,-48,-100,-62,-50,-89,120,-103,-107,-56,108,-99,9,71,52,92,-123,49,52,91,-41,-109,125,19,44,55,9,-51,102,-124,-82,-61,24,71,-96,5,85,-101,-92,25,-76,-78,48,-55,-51,71,-61,67,-103,-92,-49,6,-45,108,75,73,27,-80,-49,-62,53,-101,23,-64,-25,75,-96,89,103,72,-67,48,-44,11,-107,-83,-105,71,105,-8,-126,35,-119,29,-70,-48,74,-69,-10,-106,-18,92,-48,-98,104,122,-90,-85,48,93,10,-118,2,108,-78,-100,102,-55,38,85,46,-44,115,-27,46,-60,-123,23,-2,-106,82,18,-49,-33,-54,21,26,4,-109,-35,-86,-114,-15,107,23,-125,119,36,-125,70,-102,71,-55,23,-58,96,47,5,-60,-13,-61,-24,-80,-28,96,97,105,-31,52,-100,123,101,60,53,-61,112,33,12,48,54,19,-61,-56,74,-112,116,41,-127,-42,74,41,-28,-69,-4,34,-53,109,-68,-64,-113,17,1,-7,-3,77,-18,-8,44,-55,112,4,-39,-77,27,12,68,61,-102,-92,-23,126,112,-45,48,-64,-91,100,-67,14,-45,-76,88,11,-45,-2,-61,-75,-108,-113,-113,-13,67,0,-99,-114,12,64,-91,17,3,-128,-124,108,14,0,-46,28,-99,3,-32,104,66,0,-35,-82,12,64,-91,-111,0,48,-35,6,1,-40,-74,-54,1,-48,84,93,-120,-96,-33,-105,33,-88,52,98,4,-70,-34,96,8,116,-45,114,121,4,-70,24,-63,-27,-91,12,65,-91,-111,32,112,27,-116,-127,-127,44,-115,71,96,-70,66,4,87,87,50,4,-107,70,-116,-64,112,26,-116,-127,-87,89,54,-113,-64,21,-57,-32,-6,90,-122,-96,-46,-120,17,-104,77,34,-80,-112,-50,111,100,36,-55,-94,-31,80,-122,-96,-46,-120,17,-40,77,30,69,-74,-87,-15,89,-124,36,103,81,16,-56,16,84,26,49,2,71,111,112,31,56,-82,-55,-97,69,-70,110,10,17,-116,70,50,4,-107,70,-116,-64,117,26,68,-96,-87,-90,-31,-16,16,92,49,-124,-101,27,25,-124,74,35,-71,-110,-31,-38,108,16,3,-46,85,126,51,27,-106,56,-111,38,19,25,-122,74,35,-63,-48,-24,-99,-96,25,8,-103,-4,-61,66,-78,-99,-89,83,25,-122,74,35,-63,96,-94,38,115,-55,-46,85,-2,72,-78,52,113,28,102,51,25,-122,74,35,-63,96,55,-71,-93,53,-57,52,-8,45,109,-19,-10,-61,-61,-57,-71,-78,43,43,-90,25,-50,-74,48,57,-100,96,-73,41,-95,51,-118,-25,-49,121,93,48,25,-34,-113,6,-82,-83,-62,-3,91,124,116,-37,-123,67,-56,50,12,3,-23,-102,-19,-72,-106,-125,92,56,-25,-64,39,-16,99,-76,-51,54,-37,18,-28,106,-123,87,-60,-117,23,67,-126,-93,-76,27,1,-100,-36,-29,-68,-108,41,-86,-118,-78,18,41,94,-53,71,-75,8,91,46,-80,-50,-21,20,-74,58,-108,-32,-25,-37,-51,-2,-127,93,-82,-93,-16,69,46,20,10,94,-43,-99,127,-74,-84,84,0,31,-40,12,59,41,76,90,127,-58,-77,64,-46,112,83,-106,10,-29,105,-105,57,-73,-49,64,-107,-91,-62,-95,-55,109,-69,110,-94,-101,-24,-40,-92,55,-99,-43,76,28,-29,-40,-30,-22,-54,-81,15,-14,-15,112,28,108,-45,97,-50,82,28,-89,120,-50,122,117,9,-55,-105,120,74,-24,75,56,39,-2,19,-90,43,-112,56,-4,-117,51,47,16,-123,111,126,54,-53,-124,-64,-94,80,-78,-24,-122,36,90,-28,-21,-100,71,2,-60,53,-55,42,-65,-59,-64,-63,-63,98,76,-109,100,89,-74,-58,-112,-5,-84,116,-37,-105,-117,65,94,-65,-58,-117,-68,113,-49,-118,46,-88,-54,70,-53,86,72,-77,39,-82,79,-25,117,19,-46,-73,118,81,-39,-42,21,-125,52,-35,66,21,-99,-105,-60,-12,-83,84,6,121,-23,-122,-93,48,43,36,-112,-54,62,43,-91,-65,-66,-101,-125,-68,-64,111,-60,-49,-5,-1,-50,79,112,52,-33,-73,-5,-8,-105,45,-40,15,-20,91,-71,-79,-18,122,67,118,-78,49,-55,97,-10,6,-55,89,-47,-95,80,-18,-113,39,-106,-25,-121,-3,-81,-123,-3,107,-118,-86,80,50,-71,-34,99,-65,-27,11,123,-113,59,94,112,59,-101,-98,121,65,-5,-84,-43,-71,-13,38,94,-81,-61,-115,-90,25,-68,47,-63,-99,-60,-105,-102,66,-18,75,32,-13,37,-16,-4,-2,-24,55,93,-71,12,36,-82,92,122,-125,-32,108,-40,-15,120,127,116,-109,31,-94,-35,-110,12,-47,30,120,-83,-50,108,-32,127,110,24,95,6,-53,-9,-90,-3,-65,58,-97,89,-27,-121,-113,-4,-74,-84,81,86,-58,17,101,5,23,-54,33,101,85,-29,20,126,66,89,-63,-33,39,73,43,-3,-41,-92,85,-50,66,125,-98,-76,-54,57,-82,127,69,90,25,123,50,74,117,-10,100,-108,-128,-76,-86,-20,-64,72,64,90,33,70,90,53,-55,89,125,85,-54,7,-23,-4,-3,117,98,-108,-113,-125,-8,119,-27,-87,81,62,22,66,39,78,-7,-24,26,79,124,-98,26,-27,-125,-48,17,113,120,106,-108,-113,-61,111,-28,-109,-93,124,44,62,-117,78,-116,-14,113,-43,-93,26,-9,-28,40,31,75,-27,121,-73,19,-92,124,44,126,51,-97,32,-27,99,-13,-44,-37,9,82,62,38,127,36,-99,32,-27,-29,30,-47,86,95,-97,-14,41,-33,-14,-115,-110,62,-59,-77,-108,39,125,10,-23,79,73,-97,-39,-92,-50,-24,-120,56,-97,-33,-90,-123,12,83,-1,21,45,-92,33,1,115,116,-56,11,25,34,94,-56,-74,63,-59,11,-79,95,43,-72,119,-87,-50,-1,-112,-73,-69,-52,-66,-119,-95,-26,-35,-4,38,-122,-66,-119,-95,-1,27,49,4,-97,31,15,0,-88,84"
Is there a better Option for reducing the number of characters in a string without converting it to byte array and unwanted characters?
Thanks in advance,

You can compress to a byte[] and then encode the result in Base64. This will only use alphanumeric and fewer symbols which are safe for transfering as text. i.e. it is widely used for this.
public static void main(String[] args) {
StringBuilder sb = new StringBuilder();
while (sb.length() < 751396)
sb.append("Size: ").append(sb.length()).append("\n");
String s = sb.toString();
String s2 = deflateBase64(s);
System.out.println("Uncompressed size = " + s.length() + ", compressed size=" + s2.length());
String s3 = inflateBase64(s2);
System.out.println("Same after inflating is " + s3.equals(s));
}
public static String deflateBase64(String text) {
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
try (Writer writer = new OutputStreamWriter(new DeflaterOutputStream(baos))) {
writer.write(text);
}
return Base64.getEncoder().encodeToString(baos.toByteArray());
} catch (IOException e) {
throw new AssertionError(e);
}
}
public static String inflateBase64(String base64) {
try (Reader reader = new InputStreamReader(
new InflaterInputStream(
new ByteArrayInputStream(
Base64.getDecoder().decode(base64))))) {
StringWriter sw = new StringWriter();
char[] chars = new char[1024];
for (int len; (len = reader.read(chars)) > 0; )
sw.write(chars, 0, len);
return sw.toString();
} catch (IOException e) {
throw new AssertionError(e);
}
}
prints
Uncompressed size = 751400, compressed size=219564
Same after inflating is true

You can use the Deflater a little more:
public static byte[] compress(byte[] data) throws IOException {
new Deflater(Deflater.BEST_COMPRESSION, true);
//...
}
So you'll have the strongest compression and you'll skip some of the header data. This is the best you can do with the builtin algorithms.

Java Replace Line In Text File

How do I replace a line of text found within a text file?
I have a string such as:
Do the dishes0
And I want to update it with:
Do the dishes1
(and vise versa)
How do I accomplish this?
ActionListener al = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
JCheckBox checkbox = (JCheckBox) e.getSource();
if (checkbox.isSelected()) {
System.out.println("Selected");
String s = checkbox.getText();
replaceSelected(s, "1");
} else {
System.out.println("Deselected");
String s = checkbox.getText();
replaceSelected(s, "0");
}
}
};
public static void replaceSelected(String replaceWith, String type) {
}
By the way, I want to replace ONLY the line that was read. NOT the entire file.

At the bottom, I have a general solution to replace lines in a file. But first, here is the answer to the specific question at hand. Helper function:
public static void replaceSelected(String replaceWith, String type) {
try {
// input the file content to the StringBuffer "input"
BufferedReader file = new BufferedReader(new FileReader("notes.txt"));
StringBuffer inputBuffer = new StringBuffer();
String line;
while ((line = file.readLine()) != null) {
inputBuffer.append(line);
inputBuffer.append('\n');
}
file.close();
String inputStr = inputBuffer.toString();
System.out.println(inputStr); // display the original file for debugging
// logic to replace lines in the string (could use regex here to be generic)
if (type.equals("0")) {
inputStr = inputStr.replace(replaceWith + "1", replaceWith + "0");
} else if (type.equals("1")) {
inputStr = inputStr.replace(replaceWith + "0", replaceWith + "1");
}
// display the new file for debugging
System.out.println("----------------------------------\n" + inputStr);
// write the new string with the replaced line OVER the same file
FileOutputStream fileOut = new FileOutputStream("notes.txt");
fileOut.write(inputStr.getBytes());
fileOut.close();
} catch (Exception e) {
System.out.println("Problem reading file.");
}
}
Then call it:
public static void main(String[] args) {
replaceSelected("Do the dishes", "1");
}
Original Text File Content:
Do the dishes0
Feed the dog0
Cleaned my room1
Output:
Do the dishes0
Feed the dog0
Cleaned my room1
----------------------------------
Do the dishes1
Feed the dog0
Cleaned my room1
New text file content:
Do the dishes1
Feed the dog0
Cleaned my room1
And as a note, if the text file was:
Do the dishes1
Feed the dog0
Cleaned my room1
and you used the method replaceSelected("Do the dishes", "1");,
it would just not change the file.
Since this question is pretty specific, I'll add a more general solution here for future readers (based on the title).
// read file one line at a time
// replace line as you read the file and store updated lines in StringBuffer
// overwrite the file with the new lines
public static void replaceLines() {
try {
// input the (modified) file content to the StringBuffer "input"
BufferedReader file = new BufferedReader(new FileReader("notes.txt"));
StringBuffer inputBuffer = new StringBuffer();
String line;
while ((line = file.readLine()) != null) {
line = ... // replace the line here
inputBuffer.append(line);
inputBuffer.append('\n');
}
file.close();
// write the new string with the replaced line OVER the same file
FileOutputStream fileOut = new FileOutputStream("notes.txt");
fileOut.write(inputBuffer.toString().getBytes());
fileOut.close();
} catch (Exception e) {
System.out.println("Problem reading file.");
}
}

Since Java 7 this is very easy and intuitive to do.
List<String> fileContent = new ArrayList<>(Files.readAllLines(FILE_PATH, StandardCharsets.UTF_8));
for (int i = 0; i < fileContent.size(); i++) {
if (fileContent.get(i).equals("old line")) {
fileContent.set(i, "new line");
break;
}
}
Files.write(FILE_PATH, fileContent, StandardCharsets.UTF_8);
Basically you read the whole file to a List, edit the list and finally write the list back to file.
FILE_PATH represents the Path of the file.

If replacement is of different length:
Read file until you find the string you want to replace.
Read into memory the part after text you want to replace, all of it.
Truncate the file at start of the part you want to replace.
Write replacement.
Write rest of the file from step 2.
If replacement is of same length:
Read file until you find the string you want to replace.
Set file position to start of the part you want to replace.
Write replacement, overwriting part of file.
This is the best you can get, with constraints of your question. However, at least the example in question is replacing string of same length, So the second way should work.
Also be aware: Java strings are Unicode text, while text files are bytes with some encoding. If encoding is UTF8, and your text is not Latin1 (or plain 7-bit ASCII), you have to check length of encoded byte array, not length of Java string.

I was going to answer this question. Then I saw it get marked as a duplicate of this question, after I'd written the code, so I am going to post my solution here.
Keeping in mind that you have to re-write the text file. First I read the entire file, and store it in a string. Then I store each line as a index of a string array, ex line one = array index 0. I then edit the index corresponding to the line that you wish to edit. Once this is done I concatenate all the strings in the array into a single string. Then I write the new string into the file, which writes over the old content. Don't worry about losing your old content as it has been written again with the edit. below is the code I used.
public class App {
public static void main(String[] args) {
String file = "file.txt";
String newLineContent = "Hello my name is bob";
int lineToBeEdited = 3;
ChangeLineInFile changeFile = new ChangeLineInFile();
changeFile.changeALineInATextFile(file, newLineContent, lineToBeEdited);
}
}
And the class.
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
public class ChangeLineInFile {
public void changeALineInATextFile(String fileName, String newLine, int lineNumber) {
String content = new String();
String editedContent = new String();
content = readFile(fileName);
editedContent = editLineInContent(content, newLine, lineNumber);
writeToFile(fileName, editedContent);
}
private static int numberOfLinesInFile(String content) {
int numberOfLines = 0;
int index = 0;
int lastIndex = 0;
lastIndex = content.length() - 1;
while (true) {
if (content.charAt(index) == '\n') {
numberOfLines++;
}
if (index == lastIndex) {
numberOfLines = numberOfLines + 1;
break;
}
index++;
}
return numberOfLines;
}
private static String[] turnFileIntoArrayOfStrings(String content, int lines) {
String[] array = new String[lines];
int index = 0;
int tempInt = 0;
int startIndext = 0;
int lastIndex = content.length() - 1;
while (true) {
if (content.charAt(index) == '\n') {
tempInt++;
String temp2 = new String();
for (int i = 0; i < index - startIndext; i++) {
temp2 += content.charAt(startIndext + i);
}
startIndext = index;
array[tempInt - 1] = temp2;
}
if (index == lastIndex) {
tempInt++;
String temp2 = new String();
for (int i = 0; i < index - startIndext + 1; i++) {
temp2 += content.charAt(startIndext + i);
}
array[tempInt - 1] = temp2;
break;
}
index++;
}
return array;
}
private static String editLineInContent(String content, String newLine, int line) {
int lineNumber = 0;
lineNumber = numberOfLinesInFile(content);
String[] lines = new String[lineNumber];
lines = turnFileIntoArrayOfStrings(content, lineNumber);
if (line != 1) {
lines[line - 1] = "\n" + newLine;
} else {
lines[line - 1] = newLine;
}
content = new String();
for (int i = 0; i < lineNumber; i++) {
content += lines[i];
}
return content;
}
private static void writeToFile(String file, String content) {
try (Writer writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), "utf-8"))) {
writer.write(content);
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private static String readFile(String filename) {
String content = null;
File file = new File(filename);
FileReader reader = null;
try {
reader = new FileReader(file);
char[] chars = new char[(int) file.length()];
reader.read(chars);
content = new String(chars);
reader.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (reader != null) {
try {
reader.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
return content;
}
}

Sharing the experience with Java Util Stream
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public static void replaceLine(String filePath, String originalLineText, String newLineText) {
Path path = Paths.get(filePath);
// Get all the lines
try (Stream<String> stream = Files.lines(path, StandardCharsets.UTF_8)) {
// Do the line replace
List<String> list = stream.map(line -> line.equals(originalLineText) ? newLineText : line)
.collect(Collectors.toList());
// Write the content back
Files.write(path, list, StandardCharsets.UTF_8);
} catch (IOException e) {
LOG.error("IOException for : " + path, e);
e.printStackTrace();
}
}
Usage
replaceLine("test.txt", "Do the dishes0", "Do the dishes1");

//Read the file data
BufferedReader file = new BufferedReader(new FileReader(filepath));
StringBuffer inputBuffer = new StringBuffer();
String line;
while ((line = file.readLine()) != null) {
inputBuffer.append(line);
inputBuffer.append('\n');
}
file.close();
String inputStr = inputBuffer.toString();
// logic to replace lines in the string (could use regex here to be generic)
inputStr = inputStr.replace(str, " ");
//'str' is the string need to update in this case it is updating with nothing
// write the new string with the replaced line OVER the same file
FileOutputStream fileOut = new FileOutputStream(filer);
fileOut.write(inputStr.getBytes());
fileOut.close();

Well you would need to get a file with JFileChooser and then read through the lines of the file using a scanner and the hasNext() function
http://docs.oracle.com/javase/7/docs/api/javax/swing/JFileChooser.html
once you do that you can save the line into a variable and manipulate the contents.

just how to replace strings :) as i do
first arg will be filename second target string third one the string to be replaced instead of targe
public class ReplaceString{
public static void main(String[] args)throws Exception {
if(args.length<3)System.exit(0);
String targetStr = args[1];
String altStr = args[2];
java.io.File file = new java.io.File(args[0]);
java.util.Scanner scanner = new java.util.Scanner(file);
StringBuilder buffer = new StringBuilder();
while(scanner.hasNext()){
buffer.append(scanner.nextLine().replaceAll(targetStr, altStr));
if(scanner.hasNext())buffer.append("\n");
}
scanner.close();
java.io.PrintWriter printer = new java.io.PrintWriter(file);
printer.print(buffer);
printer.close();
}
}

compression and decompression of string data in java

I am using the following code to compress and decompress string data, but the problem which I am facing is, it is easily getting compressed without error, but the decompress method throws the following error.
Exception in thread "main" java.io.IOException: Not in GZIP format
public static void main(String[] args) throws Exception {
String string = "I am what I am hhhhhhhhhhhhhhhhhhhhhhhhhhhhh"
+ "bjggujhhhhhhhhh"
+ "rggggggggggggggggggggggggg"
+ "esfffffffffffffffffffffffffffffff"
+ "esffffffffffffffffffffffffffffffff"
+ "esfekfgy enter code here`etd`enter code here wdd"
+ "heljwidgutwdbwdq8d"
+ "skdfgysrdsdnjsvfyekbdsgcu"
+ "jbujsbjvugsduddbdj";
System.out.println("after compress:");
String compressed = compress(string);
System.out.println(compressed);
System.out.println("after decompress:");
String decomp = decompress(compressed);
System.out.println(decomp);
}
public static String compress(String str) throws Exception {
if (str == null || str.length() == 0) {
return str;
}
System.out.println("String length : " + str.length());
ByteArrayOutputStream obj=new ByteArrayOutputStream();
GZIPOutputStream gzip = new GZIPOutputStream(obj);
gzip.write(str.getBytes("UTF-8"));
gzip.close();
String outStr = obj.toString("UTF-8");
System.out.println("Output String length : " + outStr.length());
return outStr;
}
public static String decompress(String str) throws Exception {
if (str == null || str.length() == 0) {
return str;
}
System.out.println("Input String length : " + str.length());
GZIPInputStream gis = new GZIPInputStream(new ByteArrayInputStream(str.getBytes("UTF-8")));
BufferedReader bf = new BufferedReader(new InputStreamReader(gis, "UTF-8"));
String outStr = "";
String line;
while ((line=bf.readLine())!=null) {
outStr += line;
}
System.out.println("Output String lenght : " + outStr.length());
return outStr;
}
Still couldn't figure out how to fix this issue!

This is because of
String outStr = obj.toString("UTF-8");
Send the byte[] which you can get from your ByteArrayOutputStream and use it as such in your ByteArrayInputStream to construct your GZIPInputStream. Following are the changes which need to be done in your code.
byte[] compressed = compress(string); //In the main method
public static byte[] compress(String str) throws Exception {
...
...
return obj.toByteArray();
}
public static String decompress(byte[] bytes) throws Exception {
...
GZIPInputStream gis = new GZIPInputStream(new ByteArrayInputStream(bytes));
...
}

The above Answer solves our problem but in addition to that.
if we are trying to decompress a uncompressed("not a zip format") byte[] .
we will get "Not in GZIP format" exception message.
For solving that we can add addition code in our Class.
public static boolean isCompressed(final byte[] compressed) {
return (compressed[0] == (byte) (GZIPInputStream.GZIP_MAGIC)) && (compressed[1] == (byte) (GZIPInputStream.GZIP_MAGIC >> 8));
}
My Complete Compression Class with compress/decompress would look like:
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;
public class GZIPCompression {
public static byte[] compress(final String str) throws IOException {
if ((str == null) || (str.length() == 0)) {
return null;
}
ByteArrayOutputStream obj = new ByteArrayOutputStream();
GZIPOutputStream gzip = new GZIPOutputStream(obj);
gzip.write(str.getBytes("UTF-8"));
gzip.flush();
gzip.close();
return obj.toByteArray();
}
public static String decompress(final byte[] compressed) throws IOException {
final StringBuilder outStr = new StringBuilder();
if ((compressed == null) || (compressed.length == 0)) {
return "";
}
if (isCompressed(compressed)) {
final GZIPInputStream gis = new GZIPInputStream(new ByteArrayInputStream(compressed));
final BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(gis, "UTF-8"));
String line;
while ((line = bufferedReader.readLine()) != null) {
outStr.append(line);
}
} else {
outStr.append(compressed);
}
return outStr.toString();
}
public static boolean isCompressed(final byte[] compressed) {
return (compressed[0] == (byte) (GZIPInputStream.GZIP_MAGIC)) && (compressed[1] == (byte) (GZIPInputStream.GZIP_MAGIC >> 8));
}
}

If you ever need to transfer the zipped content via network or store it as text, you have to use Base64 encoder(such as apache commons codec Base64) to convert the byte array to a Base64 String, and decode the string back to byte array at remote client.
Found an example at Use Zip Stream and Base64 Encoder to Compress Large String Data!

Another example of correct compression and decompression:
#Slf4j
public class GZIPCompression {
public static byte[] compress(final String stringToCompress) {
if (isNull(stringToCompress) || stringToCompress.length() == 0) {
return null;
}
try (final ByteArrayOutputStream baos = new ByteArrayOutputStream();
final GZIPOutputStream gzipOutput = new GZIPOutputStream(baos)) {
gzipOutput.write(stringToCompress.getBytes(UTF_8));
gzipOutput.finish();
return baos.toByteArray();
} catch (IOException e) {
throw new UncheckedIOException("Error while compression!", e);
}
}
public static String decompress(final byte[] compressed) {
if (isNull(compressed) || compressed.length == 0) {
return null;
}
try (final GZIPInputStream gzipInput = new GZIPInputStream(new ByteArrayInputStream(compressed));
final StringWriter stringWriter = new StringWriter()) {
IOUtils.copy(gzipInput, stringWriter, UTF_8);
return stringWriter.toString();
} catch (IOException e) {
throw new UncheckedIOException("Error while decompression!", e);
}
}
}

The problem is this line:
String outStr = obj.toString("UTF-8");
The byte array obj contains arbitrary binary data. You can't "decode" arbitrary binary data as if it was UTF-8. If you try you will get a String that cannot then be "encoded" back to bytes. Or at least, the bytes you get will be different to what you started with ... to the extent that they are no longer a valid GZIP stream.
The fix is to store or transmit the contents of the byte array as-is. Don't try to convert it into a String. It is binary data, not text.

Client send some messages need be compressed, server (kafka) decompress the string meesage
Below is my sample:
compress:
public static String compress(String str, String inEncoding) {
if (str == null || str.length() == 0) {
return str;
}
try {
ByteArrayOutputStream out = new ByteArrayOutputStream();
GZIPOutputStream gzip = new GZIPOutputStream(out);
gzip.write(str.getBytes(inEncoding));
gzip.close();
return URLEncoder.encode(out.toString("ISO-8859-1"), "UTF-8");
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
decompress:
public static String decompress(String str, String outEncoding) {
if (str == null || str.length() == 0) {
return str;
}
try {
String decode = URLDecoder.decode(str, "UTF-8");
ByteArrayOutputStream out = new ByteArrayOutputStream();
ByteArrayInputStream in = new ByteArrayInputStream(decode.getBytes("ISO-8859-1"));
GZIPInputStream gunzip = new GZIPInputStream(in);
byte[] buffer = new byte[256];
int n;
while ((n = gunzip.read(buffer)) >= 0) {
out.write(buffer, 0, n);
}
return out.toString(outEncoding);
} catch (IOException e) {
e.printStackTrace();
}
return null;
}

You can't convert binary data to String. As a solution you can encode binary data and then convert to String. For example, look at this How do you convert binary data to Strings and back in Java?