Develop Reference

How to replace a word based on its length?

All words having the given length wordLength in the string sentence must be replaced with the word myWord. All parameters come from user input and may vary. I have tried this way but it only returns the initial string with the initial words.
Here is my source code:
package main;
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class Main {
public static void main(String[] args) throws Exception {
String sentence = "";
int wordLength = 0;
String myWord = "";
InputStreamReader is = new InputStreamReader(System.in);
BufferedReader bis = new BufferedReader(is);
System.out.println("Text input: ");
sentence = bis.readLine();
System.out.println("Word lenth to replace");
wordLength = Integer.parseInt(bis.readLine());
System.out.println("Word to replace to");
myWord = bis.readLine();
Text myText = new Text(myWord, sentence, wordLength);
myText.changeSentence();
System.out.println("New string" + myText.getSentence());
}
}
class Text {
private String mySentence;
private int charNumber;
private String wordToChange;
private String newSentence = "1.";
public Text(String wordToChange, String mySentece, int charNumber) {
this.mySentence = mySentece;
this.wordToChange = wordToChange;
this.charNumber = charNumber;
}
public String getSentence() {
return newSentence;
}
public void changeSentence() {
int firstPos = 0;
int i;
for (i = 0; i < mySentence.length(); i++) {
if (mySentence.charAt(i) == ' ') {
if (i - firstPos == charNumber) {
newSentence = newSentence.concat(wordToChange + " ");
firstPos = i + 1;
} else {
newSentence = newSentence.concat(mySentence.substring(firstPos, i + 1));
firstPos = i + 1;
}
} else if (i == mySentence.length() - 1) {
if (i - firstPos == charNumber) {
newSentence = newSentence.concat(wordToChange + " ");
firstPos = i + 1;
} else {
newSentence = newSentence.concat(mySentence.substring(firstPos, i + 1));
firstPos = i + 1;
}
}
}
}
}

I changed your code a little bit:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class Main {
public static void main(String[] args) {
String sentence = "";
int wordLenght = 0;
String myWord = "";
InputStreamReader is = new InputStreamReader(System.in);
BufferedReader bis = new BufferedReader(is);
try {
System.out.println("Text input: ");
sentence = bis.readLine();
System.out.println("Word lenth to replace");
wordLenght = Integer.parseInt(bis.readLine());
System.out.println("Word to replace to");
myWord = bis.readLine();
} catch (IOException e) {
e.printStackTrace();
}
Text myText = new Text(myWord, sentence, wordLenght);
System.out.println(myText.getChangeSentence());
}
}
class Text {
private String mySentence;
private int charNumber;
private String wordToChange;
private String newSentence = "1.";
public Text(String wordToChange, String mySentece, int charNumber) {
this.mySentence = mySentece;
this.wordToChange = wordToChange;
this.charNumber = charNumber;
}
public String getChangeSentence() {
String[] words = mySentence.split(" ");
for(int i = 0 ; i < words.length ; i++) {
if(words[i].length() == charNumber) {
words[i] = wordToChange;
}
}
for (String word : words) {
newSentence += word + " ";
}
return newSentence;
}
}
Input : This is a test
word length : 2
word to replace : ii
output: This ii a test

As I can see the only separator of words that is currently considered to appear in the input text is a single white space " ". If that's true, then the changeSentence method can be quite short. There is no need to do parse the sentence character by characted. Having in mind that the white space is a separator, you can simply split the sentence by the characted " " and collect them as words. After that you can just iterate through words and replace ones that lenght matches given input characters number. After that, you can just join words together with the previously used separator and that's it.
Examples if you want to try with loops
public void changeSentence() {
final String[] words = mySentence.split(" ");
for (int i = 0; i < words.length; i++) {
if (words[i].length() == charNumber) {
words[i] = wordToChange;
}
}
newSentence = String.join(" ", words);
}
or with regular expressions
public void changeSentence() {
String regex = "\\b\\w{" + charNumber+ "}\\b";
newSentence = mySentence.replaceAll(regex, wordToChange);
}
or with the stream API
public void changeSentence() {
newSentence = Arrays.stream(mySentence.split(" "))
.map(s -> s.length() == charNumber ? wordToChange : s)
.collect(Collectors.joining(" "));
}

Replace word in Java

There is some line, for example "1 qqq 4 aaa 2" and list {aaa, qqq}. I must change all words (consists only from letters) on words from list. Answer on this example "1 aaa 4 qqq 2". Try
StringTokenizer tokenizer = new StringTokenizer(str, " ");
while (tokenizer.hasMoreTokens()){
tmp = tokenizer.nextToken();
if(tmp.matches("^[a-z]+$"))
newStr = newStr.replaceFirst(tmp, words.get(l++));
}
But it's not working. In result I have the same line.
All my code:
String space = " ", tmp, newStr;
Scanner stdin = new Scanner(System.in);
while (stdin.hasNextLine()) {
int k = 0, j = 0, l = 0;
String str = stdin.nextLine();
newStr = str;
List<String> words = new ArrayList<>(Arrays.asList(str.split(" ")));
words.removeIf(new Predicate<String>() {
#Override
public boolean test(String s) {
return !s.matches("^[a-z]+$");
}
});
Collections.sort(words);
StringTokenizer tokenizer = new StringTokenizer(str, " ");
while (tokenizer.hasMoreTokens()){
tmp = tokenizer.nextToken();
if(tmp.matches("^[a-z]+$"))
newStr = newStr.replaceFirst(tmp, words.get(l++));
}
System.out.printf(newStr);
}

I think the problem might be that replaceFirst() expects a regular expression as first parameter and you are giving it a String.
Maybe try
newStr = newStr.replaceFirst("^[a-z]+$", words.get(l++));
instead?
Update:
Would that be a possibility for you:
StringBuilder _b = new StringBuilder();
while (_tokenizer.hasMoreTokens()){
String _tmp = _tokenizer.nextToken();
if(_tmp.matches("^[a-z]+$")){
_b.append(words.get(l++));
}
else{
_b.append(_tmp);
}
_b.append(" ");
}
String newStr = _b.toString().trim();
Update 2:
Change the StringTokenizer like this:
StringTokenizer tokenizer = new StringTokenizer(str, " ", true);
That will also return the delimiters (all the spaces).
And then concatenate the String like this:
StringBuilder _b = new StringBuilder();
while (_tokenizer.hasMoreTokens()){
String _tmp = _tokenizer.nextToken();
if(_tmp.matches("^[a-z]+$")){
_b.append(words.get(l++));
}
else{
_b.append(_tmp);
}
}
String newStr = _b.toString().trim();
That should work.
Update 3:
As #DavidConrad mentioned StrinkTokenizer should not be used anymore. Here is another solution with String.split():
final String[] _elements = str.split("(?=[\\s]+)");
int l = 0;
for (int i = 0; i < _tokenizer.length; i++){
if(_tokenizer[i].matches("^[a-z]+$")){
_b.append(_arr[l++]);
}
else{
_b.append(_tokenizer[i]);
}
}

Just out of curiosity, another solution (the others really don't answer the question), which takes the input line and sorts the words alphabetically in the result, as you commented in your question.
public class Replacer {
public static void main(String[] args) {
Replacer r = new Replacer();
Scanner in = new Scanner(System.in);
while (in.hasNextLine()) {
System.out.println(r.replace(in.nextLine()));
}
}
public String replace(String input) {
Matcher m = Pattern.compile("([a-z]+)").matcher(input);
StringBuffer sb = new StringBuffer();
List<String> replacements = new ArrayList<>();
while (m.find()) {
replacements.add(m.group());
}
Collections.sort(replacements);
m.reset();
for (int i = 0; m.find(); i++) {
m.appendReplacement(sb, replacements.get(i));
}
m.appendTail(sb);
return sb.toString();
}
}

Multiline strings concatenation in Java

I'm looking for some help. What is the easiest way to concatenate multiline strings in Java and print it after ?
For example : I've got two strings :
String turtle1 = " _\r\n .-./*)\r\n _/___\\/\r\n U U\r";
String turtle2 = " _\r\n .-./*)\r\n _/___\\/\r\n U U\r";
And I want to get this result in the Java Eclipse console :
_ _
.-./*) .-./*)
_/___\/ _/___\/
U U U U
I've already try some algorithms to divide my strings in differents parts and after re-concatenate it. But it was without success.
I know there are StringBuffer class and StringBuilder class but after some research, I didn't found something that correspond to my need.
Thanks in advance for your help.

See my example below, should be self explaining.
public class Turtle {
private static final String returnpattern = "\r\n";
public static void main(String[] args) {
// the data to run through
String turtle1 = " _\r\n .-./*)\r\n _/___\\/\r\n U U\r\n";
String turtle2 = " _\r\n .-./*)\r\n _/___\\/\r\n U U\r\n";
// split the data into individual parts
String[] one = turtle1.split(returnpattern);
String[] two = turtle2.split(returnpattern);
// find out the longest String in data set one
int longestString = 0;
for (String s : one) {
if (longestString < s.length()) {
longestString = s.length();
}
}
// loop through parts and build new string
StringBuilder b = new StringBuilder();
for (int i = 0; i < one.length; i++) {
String stringTwo = String.format("%1$" + longestString + "s", two[i]); // left pad the dataset two to match
// length
b.append(one[i]).append(stringTwo).append(returnpattern);
}
// output
System.out.println(b);
}
}

Just for fun, here is another solution using streams, prepared for more than two turtles to be shown side-by-side:
public static void main(String[] args) {
String turtle1 = " _\r\n .-./*)\r\n _/___\\/\r\n U U\r";
String turtle2 = " _\r\n .-./*)\r\n _/___\\/\r\n U U\r";
// split lines into fragments
List<List<String>> fragments = Stream.of(turtle1, turtle2)
.map(x -> Stream.of(x.split("\\r\\n?|\\n")).collect(Collectors.toList()))
.collect(Collectors.toList());
// make all lists same length by adding empty lines as needed
int lines = fragments.stream().mapToInt(List::size).max().orElse(0);
fragments.forEach(x -> x.addAll(Collections.nCopies(lines - x.size(), "")));
// pad all fragments to maximum width (per list)
List<List<String>> padded = fragments.stream().map(x -> {
int width = x.stream().mapToInt(String::length).max().orElse(0);
return x.stream().map(y -> String.format("%-" + width + "s", y)).collect(Collectors.toList());
}).collect(Collectors.toList());
// join corresponding fragments to result lines, and join result lines
String result = IntStream.range(0, lines)
.mapToObj(i -> padded.stream().map(x -> x.get(i)).collect(Collectors.joining()))
.collect(Collectors.joining(System.lineSeparator()));
System.out.println(result);
}

Not so pretty but works:
String turtle1 = " _\r\n .-./*)\r\n _/___\\/\r\n U U\r\n";
String turtle2 = " _\r\n .-./*)\r\n _/___\\/\r\n U U\r\n";
String[] turtle1Lines = turtle1.split("\r\n");
String[] turtle2Lines = turtle2.split("\r\n");
StringBuilder sb = new StringBuilder();
int turtle1Width = 0;
for (int i = 0; i < 4; i++) {
if (turtle1Lines[i].length() > turtle1Width) {
turtle1Width = turtle1Lines[i].length();
}
}
for (int i = 0; i < 4; i++) {
sb.append(turtle1Lines[i]);
for (int j = turtle1Width - turtle1Lines[i].length(); j > 0; j--) {
sb.append(' ');
}
sb.append(turtle2Lines[i]);
sb.append("\r\n");
}
String turtles = sb.toString();

I'm here too ;)
public class Test {
static String turtle1 = " _\r\n .-./*)\r\n _/___\\/\r\n U U\r".replace("\r", "");
static String turtle2 = " _\r\n .-./*)\r\n _/___\\/\r\n U U\r".replace("\r", "");
public static int countRows(String string){
return string.length() - string.replace("\n", "").length() + 1;
}
public static int getMaxLength(String string){
int maxLength = 0;
int currentLength = 0;
char[] data = string.toCharArray();
for(Character c : data){
if(c != '\n'){
if(++currentLength > maxLength) {
maxLength = currentLength;
}
}else{
currentLength = 0;
}
}
return maxLength;
}
public static String[] toStringArray(String string){
int length = getMaxLength(string);
int rows = countRows(string);
String[] result = new String[rows];
int last = 0;
for(int i = 0; i < rows; i++){
int temp = string.indexOf("\n", last);
String str;
if(temp != -1) {
str = string.substring(last, temp);
}else{
str = string.substring(last);
}
while(str.length() < length){
str += " ";
}
result[i] = str;
last = temp + 1;
}
return result;
}
public static String concatMultilineStrings(String first, String second){
StringBuilder sb = new StringBuilder();
String[] arrayFirst = toStringArray(first);
String[] arraySecond = toStringArray(second);
if(arrayFirst.length != arraySecond.length){
System.exit(69);
}
for(int i = 0; i < arrayFirst.length; i++){
sb.append(arrayFirst[i]);
sb.append(arraySecond[i]);
sb.append("\n");
}
return sb.toString();
}
public static void main(String[] args) {
System.out.println(concatMultilineStrings(turtle1, turtle2));
}
}

The program throws NullPointerException [closed]

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Closed 8 years ago.
Improve this question
Not sure why it gives me the NullPointerException. Please help.
I am pretty sure all the arrays are full, and i restricted all the loops not to go passed empty spaces.
import java.util.;
import java.io.;
public class TextAnalysis {
public static void main (String [] args) throws IOException {
String fileName = args[0];
File file = new File(fileName);
Scanner fileScanner = new Scanner(file);
int MAX_WORDS = 10000;
String[] words = new String[MAX_WORDS];
int unique = 0;
System.out.println("TEXT FILE STATISTICS");
System.out.println("--------------------");
System.out.println("Length of the longest word: " + longestWord(fileScanner));
read(words, fileName);
System.out.println("Number of words in file wordlist: " + wordList(words));
System.out.println("Number of words in file: " + countWords(fileName) + "\n");
System.out.println("Word-frequency statistics");
lengthFrequency(words);
System.out.println();
System.out.println("Wordlist dump:");
wordFrequency(words,fileName);
}
public static void wordFrequency(String[] words, String fileName) throws IOException{
File file = new File(fileName);
Scanner s = new Scanner(file);
int [] array = new int [words.length];
while(s.hasNext()) {
String w = s.next();
if(w!=null){
for(int i = 0; i < words.length; i++){
if(w.equals(words[i])){
array[i]++;
}
}
for(int i = 0; i < words.length; i++){
System.out.println(words[i] + ":" + array[i]);
}
}
}
}
public static void lengthFrequency (String [] words) {
int [] lengthTimes = new int[10];
for(int i = 0; i < words.length; i++) {
String w = words[i];
if(w!=null){
if(w.length() >= 10) {
lengthTimes[9]++;
} else {
lengthTimes[w.length()-1]++;
}
}
}
for(int j = 0; j < 10; j++) {
System.out.println("Word-length " + (j+1) + ": " + lengthTimes[j]);
}
}
public static String longestWord (Scanner s) {
String longest = "";
while (s.hasNext()) {
String word = s.next();
if (word.length() > longest.length()) {
longest = word;
}
}
return (longest.length() + " " + "(\"" + longest + "\")");
}
public static int countWords (String fileName) throws IOException {
File file = new File(fileName);
Scanner fileScanner = new Scanner(file);
int count = 0;
while(fileScanner.hasNext()) {
String word = fileScanner.next();
count++;
}
return count;
}
public static void read(String[] words, String fileName) throws IOException{
File file = new File(fileName);
Scanner s = new Scanner(file);
while (s.hasNext()) {
String word = s.next();
int i;
for ( i=0; i < words.length && words[i] != null; i++ ) {
words[i]=words[i].toLowerCase();
if (words[i].equals(word)) {
break;
}
}
words[i] = word;
}
}
public static int wordList(String[] words) {
int count = 0;
while (words[count] != null) {
count++;
}
return count;
}
}

There are two problems with this code
1.You didn't do null check,although the array contains null values
2.Your array index from 0-8,if you wan't to get element at 9th index it will throw ArrayIndexOutOfBound Exception.
Your code should be like that
public static void lengthFrequency (String [] words) {
int [] lengthTimes = new int [9];
for(int i = 0; i < words.length; i++) {
String w = words[i];
if(null!=w) //This one added for null check
{
/* if(w.length() >= 10) {
lengthTimes[9]++;
} else {
lengthTimes[w.length()-1]++;
}
}*/
//Don't need to check like that ...u can do like below
for(int i = 0; i < words.length; i++) {
String w = words[i];
if(null!=w)
{
lengthTimes[i] =w.length();
}
}
}
//here we should traverse upto length of the array.
for(int i = 0; i < lengthTimes.length; i++) {
System.out.println("Word-length " + (i+1) + ": " + lengthTimes[i]);
}
}

Your String Array String[] words = new String[MAX_WORDS]; is not initialized,you are just declaring it.All its content is null,calling length method in line 31 will give you null pointer exception.
`

Simple mistake. When you declare an array, it is from size 0 to n-1. This array only has indexes from 0 to 8.
int [] lengthTimes = new int [9];
//some code here
lengthTimes[9]++; // <- this is an error (this is line 29)
for(int i = 0; i < 10; i++) {
System.out.println("Word-length " + (i+1) + ": " + lengthTimes[i]); // <- same error when i is 9. This is line 37

When you declare:
String[] words = new String[MAX_WORDS];
You're creating an array with MAX_WORDS of nulls, if your input file don't fill them all, you'll get a NullPointerException at what I think is line 37 in your original file:
if(w.length() >= 10) { // if w is null this would throw Npe
To fix it you may use a List instead:
List<String> words = new ArrayList<String>();
...
words.add( aWord );
Or perhaps you can use a Set if you don't want to have repeated words.

Java StringTokenizer

I have the following input
(11,C) (5,) (7,AB)
I need to split them into 2 part for each coordinates.
So my intarray should have 11, 5, 7
and my letter array should have C,,AB
But when I try using stringtokenizer,
I only get my intarray should have 11, 5, 7
and my letter array should have C,AB
Is there any way I could get the empty part of (5,)?
Thank you.
Vector<String> points = new Vector<String> ();
String a = "(11,C) (5,) (7,AB)";
StringTokenizer st = new StringTokenizer(a, "(,)");
while(st.hasMoreTokens()) {
points.add(st.nextToken());
}
}
System.out.println(points);

List <Integer> digits = new ArrayList <Integer> ();
List <String> letters = new ArrayList <String> ();
Matcher m = Pattern.compile ("\\((\\d+),(\\w*)\\)").matcher (string);
while (m.find ())
{
digits.add (Integer.valueOf (m.group (1)));
letters.add (m.group (2));
}

Must be like this
String[] values = a.split("\\) \\(");
String[][] result = new String[values.length][2];
for (int i = 0; i < values.length; i++) {
values[i] = values[i].replaceAll("\\(|\\)", "") + " ";
result[i] = values[i].split("\\,");
System.out.println(result[i][0] + " * " + result[i][1]);
}
result will contain coordinate pairs.

public static void main(String[] args) {
String s = "(11,C), (5,) ,(7,AB)";
ArrayList<String> name = new ArrayList<String>();
ArrayList<Integer> number = new ArrayList<Integer>();
int intIndex = 0, stringIndex = 0;
String[] arr = s.split(",");
for (int i = 0; i < arr.length; i++) {
String ss = arr[i].replace("(", "");
ss = ss.replace(")", "");
boolean b = isNumeric(ss);
// System.out.println( Arrays.toString(arr));
if (b) {
int num = Integer.valueOf(ss.trim()).intValue();
number.add(num);
} else
name.add(ss);
}
System.out.println(name);
System.out.println(number);
}
public static boolean isNumeric(String str) {
try {
double d = Double.parseDouble(str);
} catch (NumberFormatException nfe) {
return false;
}
return true;
}
Try this: I have slightly changed the input from "(11,C) (5,) (7,AB)" to "(11,C), (5,) ,(7,AB)" .
Output:
[C, , AB]
[11, 5, 7]

Brutal coding, in raw level:
List<String> points = new ArrayList<String> ();
String source= "(11,C) (5,) (7,AB)";
StringTokenizer deleteLeft = new StringTokenizer(source, "(");
while(deleteLeft.hasMoreTokens()) {
StringTokenizer deleteRight = new StringTokenizer(deleteLeft.nextToken(), ")");
points.add(deleteRight.nextToken());
}
System.out.println(points);
}