I am working in school project. In that what they told is, I will be given a String which contains an actual program like....
import java.io.*\npublic class A{\n...........EOF
And My job is to find particular regular expressions in that String(Program).
Now My question is..
void myFunc(String s)
{
while(s.charAt(i) != EOF) /*needed replacement for EOF*/
{
// Actual Code
}
}
In the above code, how to find whether EOF is reached in a string?
It's unlikely that you need this - you probably just need to read till the end of the string, and since it's a representation of a file's contents, your teacher referred to it as EOF.
However...
There is a character called EOF. It's also called control-Z, because that's how you type it. If you want to include it in a string, you have to type it as "\u001a" as in:
String iHaveAnEof = "file ends here\u001a";
If you really need this, your teacher is probably older than me, and I'm probably old enough to be your grandfather ;-)
There is no EOF character in a string. You just need to iterate over the characters in the string:
for (int i = 0; i < s.length(); i++){
char c = s.charAt(i);
//Process char
}
BufferedReader rd=new BufferedReader(new InputStreamReader(new FileInputStream("Input.txt"),"UTF-8"));
char ch;
int r;
while(true)
{
r=rd.read(); //Reading a character in integer format
if(r==-1) //Checking for the End of File
break;
else
{
ch=(char)r; //Converting to char format
System.out.println(ch);
}
}
Related
I have a raw txt file with delimiters which i use to split text. To receive text I use scanner:
int textid = getResources().getIdentifier(word, null, this.getPackageName());
Scanner ch = new Scanner(getResources().openRawResource(textid));
Opened file is correct. When I begin receiving information I need to read it until "$" is got.
while (ch.hasNext()) {
str = ch.next();
boolean flag = (str.equals("$"));
while (!(str.equals("$"))) {
str = ch.next();
}
The problem is that when str equals "$" (Checked it through breakpoint) flag equals "false". However, if I initialize String m = "$" and check flag = m.equals("$")flag equals "true". Also tried to use str != "$" but it didn't help.
My guess is that scanner.next() returns another type but it seems to be rather strange.
This might help you.
First next() reads multiple characters until whitespace is found.
Go through every char in str to see if its the '$'. Then when you find it do whatever you wanted to do.
while (ch.hasNext()) {
String str = ch.next();
for(int i = 0; i<str.length(); i++) {
if(str.charAt(i) == '$') {
//do something
}
}
}
When your code reads a "$", it will break the inner loop. When it starts over the outer loop, you're calling ch.next() again, which overwrites the previous "$"in str. This might be the reason why flag is set to false. It would detect the "$" only if it's the first thing in the file.
Also, you might want to check ch.hasNext() in the inner loop again.
I am trying to write one java program. This program take a string from the user as an input and display the output by removing the special characters in it. And display the each strings in new line
Let's say I have this string Abc#xyz,2016!horrible_just?kidding after reading this string my program should display the output by removing the special characters like
Abc
xyz
2016
horrible
just
kidding
Now I know there are already API available like Matcher and Patterns API in java to do this. But I don't want to use the API since I am a beginner to java so I am just trying to crack the code bit by bit.
This is what I have tried so far. What I have done here is I am taking the string from the user and stored the special characters in an array and doing the comparison till it get the special character. And also storing the new character in StringBuilder class.
Here is my code
import java.util.*;
class StringTokens{
public void display(String string){
StringBuilder stringToken = new StringBuilder();
stringToken.setLength(0);
char[] str = {' ','!',',','?','.','_','#'};
for(int i=0;i<string.length();i++){
for(int j =0;j<str.length;j++){
if((int)string.charAt(i)!=(int)str[j]){
stringToken.append(str[j]);
}
else {
System.out.println(stringToken.toString());
stringToken.setLength(0);
}
}
}
}
public static void main(String[] args){
if(args.length!=1)
System.out.println("Enter only one line string");
else{
StringTokens st = new StringTokens();
st.display(args[0]);
}
}
}
When I run this code I am only getting the special characters, I am not getting the each strings in new line.
One easy way - use a set to hold all invalid characters:
Set<Character> invalidChars = new HashSet<>(Arrays.asList('$', ...));
Then your check boils down to:
if(invaidChars.contains(string.charAt(i)) {
... invalid char
} else {
valid char
}
But of course, that still means: you are re-inventing the wheel. And one does only re-invent the wheel, if one has very good reasons to. One valid reason would be: your assignment is to implement your own solution.
But otherwise: just read about replaceAll. That method does exactly what your current code; and my solution would be doing. But in a straight forward way; that every good java programmer will be able to understand!
So, to match your question: yes, you can implement this yourself. But the next step is to figure the "canonical" solution to the problem. When you learn Java, then you also have to focus on learning how to do things "like everybody else", with least amount of code to solve the problem. That is one of the core beauties of Java: for 99% of all problems, there is already a straight-forward, high-performance, everybody-will-understand solution out there; most often directly in the Java standard libraries themselves! And knowing Java means to know and understand those solutions.
Every C coder can put down 150 lines of low-level array iterating code in Java, too. The true virtue is to know the ways of doing the same thing with 5 or 10 lines!
I can't comment because I don't have the reputation required. Currently you are appending str[j] which represents special character. Instead you should be appending string.charAt(i). Hope that helps.
stringToken.append(str[j]);
should be
stringToken.append(string.charAt(i));
Here is corrected version of your code, but there are better solutions for this problem.
public class StringTokens {
static String specialChars = new String(new char[]{' ', '!', ',', '?', '.', '_', '#'});
public static void main(String[] args) {
if (args.length != 1) {
System.out.println("Enter only one line string");
} else {
display(args[0]);
}
}
public static void display(String string) {
StringBuilder stringToken = new StringBuilder();
stringToken.setLength(0);
for(char c : string.toCharArray()) {
if(!specialChars.contains(String.valueOf(c))) {
stringToken.append(c);
} else {
stringToken.append('\n');
}
}
System.out.println(stringToken);
}
}
public static void main(String[] args) {
String a=",!?#_."; //Add other special characters too
String test="Abc#xyz,2016!horrible_just?kidding"; //Make this as user input
for(char c : test.toCharArray()){
if(a.contains(c+""))
{
System.out.println(); //to avoid printing the special character and to print newline
}
else{
System.out.print(c);
}
}
}
you can run a simple loop and check ascii value of each character. If its something other than A-Z and a-z print newline skip the character and move on. Time complexity will be O(n) + no extra classes used.
String str = "Abc#xyz,2016!horrible_just?kidding";
char charArray[] = str.toCharArray();
boolean flag=true;;
for (int i = 0; i < charArray.length; i++) {
int temp2 = (int) charArray[i];
if (temp2 >= (int) 'A' && temp2 <= (int) 'Z') {
System.out.print(charArray[i]);
flag=true;
} else if (temp2 >= (int) 'a' && temp2 <= (int) 'z') {
System.out.print(charArray[i]);
flag=true;
} else {
if(flag){
System.out.println("");
flag=false;
}
}
}
Hi im having this assignment that I don't really understand how to pull off.
Ive been programing java for 2.5 weeks so Im really new.
Im supposed to import a text document into my program and then do these operations, count letters, sentences and average length of words. I've to perform the counting task letter by letter, I'm not allowed to scan the entire document at the same time. Ive managed to import the text and also print it out, but my problem is I cant use my string "line" to do any of these operations. Ive tried converting it to arrays, strings and after a lot of failed attempts im giving up. So how do I convert my input to something I can use, because i always get the error message "line is not a variable" or smth like that.
Jesper
UPDATE WITH MY SOLUTION! also some of it is in Swedish, sorry for that.
Somehow the Format is wrong so I uploaded the code here instead, really don't feel to argue with this wright now!
http://txs.io/3eIb
To count letters, check each character. If it's a space or punctuation, ignore it. Otherwise, it's a letter and we should this increment.
Every word should have a space after it unless it is the last word of the sentence. To get the number of words, track the number of spaces + number of sentences. To get number of sentences, find the number of ! ? and .
I would do that by looking at the ascii value of each character.
int numSentences = 0;
int numWords = 0;
while (line = ...){
for(int i = 0; i <line.length(); i++){
int curCharAsc = (int)(line.at(i)) //get ascii value by casting char to int
if((curCharAsc >= 65 && curCharAsc <= 90) || (curCharAsc >= 97 && curCharAsc <= 122) //check if letter is uppercase or lowercase
numLetters++;
if(curCharAsc == 32){ //ascii for space
numWords++;
}
else if (curCharAsc == 33 || curCharAsc == 46 || curCharAsc == 63){
numWords++;
numSentences++;
}
}
}
double avgWordLength = ((double)(letters))/numWords; //cast to double before dividing to avoid round-off
Your code as presented works fine, it loads a file and prints out the contents line by line. What you probably need to do is capture each of those lines. Java has two useful classes for this StringBuilder or StringBuffer (pick one).
BufferedReader input = new BufferedReader(new FileReader(args[0]));
String line;
StringBuffer buffer = new StringBuffer();
while ((line = input.readLine()) != null) {
System.out.println(line);
buffer.append(line+" ");
}
input.close();
performOperations(buffer.toString());
The only other possibility is (if your own code is not running for you) - possibly you aren't passing the input file name as a parameter when you run this class?
UPDATE
NB - I've modified the line
buffer.append(line+"\n");
to add a space instead of a line break, so that it is compatible with algorithms in the #faraza answer
The method performOperations doesn't exist yet. So you should / could add something like this
public static void performOperations(String data){
}
You method could in turn make calls out to separate methods for each operation
public static void performOperations(String data){
countWords(data);
countLetters(data);
averageWordLength(data);
}
To take it to the next level, and introduce Object Orientation, you could create a class TextStatsCollector.
public class TextStatsCollector{
private final String data;
public TextStatsCollector(final String data) {
this.data = data;
}
public int countWords(){
//word count impl here
}
public int countLetters(){
//letter count impl here
}
public int averageWordLength(){
//average word length impl here
}
public void performOperations(){
System.out.println("Number of Words is " + countWords());
System.out.println("Number of Letters is " + countLetters());
System.out.println("Average word length is " + averageWordLength());
}
}
Then you could use TextStatsCollector like the following in your main method
new TextStatsCollector(buffer.toString()).performOperations();
I am making a Pi based RNG(Random Number Generator) for a research project. I am getting stumped at this point hence I cant seem to figure out how to read the digits form a rather large file (1GB). Here is the input:
....159265358979323846264338327950288419716939937510582097494459230781640628620899862803482534211706798214808651328230664709384460955058223172535940812848111745028410270193852110555964462294895493038196442881097566593344612847564823378678316527120190914564856692346034861045432664821339360726024914127372458700660631558817488152092096282925409171536436789259036001133053054882046652138414695194151160943305727036575959195309218611738193261179310511854807446237996274956735188575272489122793818301194912983367336244065664308602139494639522473719070217986094370277053921717629317675238467481846766940513200056812714526356082778577134275778960917363717872146844090122495343014654958537105079227968925892354201995611212902196086403441815981362977477130996051870721134999999837297804995105973173281609631859502445945534690830264252230825334468503526193118817101000313783875288658753320838142061717766914730359825349042875546873115956286388235378759375195778185778053217122680661300192787661119590921642019893809525720106548586327886593615338182....
File is ugly I know... its Pi to 1 Billionth decimal place. I am not going into details on why I am doing this but here is my goal. I want to be able to skip x number of decimal places before beginning printing output, I also need to be able to read out y number of consecutive digits at a time so like if it was 4 at a time output would look like:
1111\n
2222\n
3333\n
4444\n....
My base objective is to be able to print at least 1 number at a time hence after that I can piece them together how I want... So basic output is:
For input 3.1415.. I get..
3,1,4,1,5....
I tried bunch of File Streams from Java API but it only prints bytes/bits... I have no idea on how to convert them to something meaningful.
Also, Reading line by line is not optimal hence I have to have my numbers be same length and I feel like reading line by line would cut them off in a funny way..
What you need is a character stream, basically a subclass of Reader, so you can read character by character, rather than byte by byte.
To achive what you need, you will have to:
List item
open a character stream to the file containing your input digits. Prefer a BufferedReader over a FileReader to speed up the I/O, since reading char by char can be very slow, especially with large files
you will need to keep track of the previous character read (if any) and group strings of identical characters in an appropriate data strcuture (for instance a StringBuilder)
if you need to skip the first n characters, use Reader.skip(n); at the start
The following code does exactly what I understand of your requirements:
public class Test {
public static void main(String[] args) {
final char decimalSeparator = ',';
try (Reader reader = new BufferedReader(new FileReader("pi.txt"))) {
int prevC = -1; // previous character read from the stream
int c; // latest character read from the stream
StringBuilder sb = new StringBuilder();
while ((c = reader.read()) != -1) {
// if first digit or same as previous digit
if ((prevC == -1) || (c == prevC)) {
sb.append((char) c);
} else {
// print the group of digits and reset sb
if (sb.length() > 0) {
System.out.println(sb.toString());
sb = new StringBuilder();
}
sb.append((char) c);
}
prevC = c;
}
// print the last digits group
if (sb.length() > 0) {
System.out.println(sb.toString());
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
Okay I have spoken to a CS professor and it seems that I have forgotten my basic Java training. 1Byte = 1 char. In this case BufferedInputReader spits out ASCII values for said chars. Here is simple solution:
FileInputStream ifs = new FileInputStream(pi); //Input File containing 1 billion digits
BufferedInputStream bis = new BufferedInputStream(ifs);
System.out.println((char)bis.read()); //Build strings or parse chars how you want
..Rinse and repeat. Sorry for wasting time... but I hope this will set someone one the right track down the road.
My program reads lines from a plain text file w/ lines formatted: <integer>;<integer>%n, where ; is the delimiter. It compares the two parsed integers against 2 other known values and increments tallyArray[i] if they match.
I currently use:
try {
scan = new Scanner(new BufferedReader(new FileReader("LogFileToBeRead.txt")));
for (int i = 0; i < tallyArraySize; i++) {
explodedLogLine = scan.nextLine().split(";");
if (IntReferenceVal1 == Integer.parseInt(explodedLogLine[0]) && IntReferenceVal2 == Integer.parseInt(explodedLogLine[1])) {
tallyArray[i]++;
}
}
} finally {
if (scan != null) { scan.close(); }
}
I was wondering if there were any serious faults with this method. It does not need to be production-quality.
Also, is there a standard way of parsing a string like this?
EDIT: We can assume the text file is perfectly formatted. But I see the importance for accounting for possible exceptions.
You are not handling NumberFormatExceptions thrown by the Integer.parseInt() method calls. If there's one bad line, execution exits your for loop.
You aren't vetting the integrity of the file you are reading from. If there isn't a ; character or if the Strings aren't actually numbers, execution simply exits the code block you posted.
If you can assume the file is perfectly formatted, and you're set on using a Scanner, you can add ; as a delimiter to the Scanner:
scan = new Scanner(new BufferedReader(new FileReader("LogFileToBeRead.txt")));
scan.useDelimiter(Pattern.compile("(;|\\s)"));
for (int i = 0; i < tallyArraySize; i++) {
int ref1 = scan.nextInt();
int ref2 = scan.nextInt();
if (IntReferenceVal1 == ref1 &&
IntReferenceVal2 == ref2) {
tallyArray[i]++;
}
}
And simply call Scanner.nextInt() twice for each line.
According to me There are three flaws in the program.
Delimiter ; what if there is delimiter is removed by accident or added by accident
There should be check on explodedLogLine that it is of length 2 and it is not null otherwise it will result in unexpected runtime error
You should catch NumberFormatException format exception since you can never be sure that Input is always a number
A simple illustration below gives you idea how things will go wrong.
String str = "3;;3";
System.out.println(Arrays.toString(str.split(";")));
This code will print [3, , 3] in such case your program will produce NumberFormatException as "" string can not be parsed to Integer.