readLine()

[prometheuzz]

...

if(a == b) //Is this correct way to compare 2 lines that have BigInteger numbers?

...

No. Only primitives can be compared for equality with the '==' operator. When comparing Objects, you should use their equals(...) method:
[CODE=java]if(a.equals(b)) {
// ...
}[/CODE]

[shana07]

Don't compare two Strings for equality using the '==' operaror. Use the member
method equals() instead; e.g. if two distinct Strings a and b both point to two
distinct String values "foo" a == b will return false while a.equals(b) returns true.

kind regards,

Jos

Thank you Jos...I am learning...
btw, why 'foo' is so sinonimn in java?
it's like so many examples about foo...why :)

[shana07]

No. Only primitives can be compared for equality with the '==' operator. When comparing Objects, you should use their equals(...) method:
[CODE=java]if(a.equals(b)) {
// ...
}[/CODE]

Thank you prometheuzz...y ou guys responded at the same time...cool!.
the equals and counter work fine!

[shana07]

I hope this would be my last question about file's....

Below is my input file (sample):

1 : 30 2
1 : 134 10
2 : 35 2
4 : 30 2
4 : 80 8
..../many more lines

How to delete the same fileno (fileno refers to the first array in line) and take only the first line for the same fileno?
Something like this:

if filenoLine1 == filenoLine2 {
print fileno1
else
print filenoLine1
print filenoLine2


So I will write and get new output file like this:

1 : 30 2
2 : 35 2
4 : 30 2

How's the syntax looks like yeah?

while((lineFRST != null) && (lineSEC != null))  
{	
    printWriter = new PrintWriter( new FileWriter("OutputFile.txt", true));
        	
    String[] thelineFRST = lineFRST.split(" ");
    String fileNo1 = thelineFRST[0];
            
    String[] thelineSEC = lineSEC.split(" ");
    String fileNo2 = thelineSEC[0];
           
            if(fileNo1.equals(fileNo2))  
            {
               printWriter.println(lineFRST); 
            }
            else
            {  
            	printWriter.println(lineFRST); 
            	printWriter.println(lineSEC); 
            }
                    
            printWriter.close();
             
            lineFRST = in1.readLine(); 
            lineSEC = in1.readLine(); 
        }  
       
         in1.close();

Problem here is - Read from one file, read 2 lines one short, compare then move them to next two lines...I will miss some equal lines if keep moving two lines one short...again kindly teach me...thank you

[prometheuzz]

Thank you Jos...I am learning...
btw, why 'foo' is so sinonimn in java?
it's like so many examples about foo...why :)

Have a look at this wiki page:

http://en.wikipedia.org/wiki/Foo

[shana07]

Have a look at this wiki page:
http://en.wikipedia.org/wiki/Foo

Now I got it why....tq

[javaalien]

I hope this would be my last question about file's....

Below is my input file (sample):

1 : 30 2
1 : 134 10
2 : 35 2
4 : 30 2
4 : 80 8
..../many more lines

How to delete the same fileno (fileno refers to the first array in line) and take only the first line for the same fileno?
Something like this:

if filenoLine1 == filenoLine2 {
print fileno1
else
print filenoLine1
print filenoLine2


So I will write and get new output file like this:

1 : 30 2
2 : 35 2
4 : 30 2

How's the syntax looks like yeah?

while((lineFRST != null) && (lineSEC != null))  
{	
    printWriter = new PrintWriter( new FileWriter("OutputFile.txt", true));
        	
    String[] thelineFRST = lineFRST.split(" ");
    String fileNo1 = thelineFRST[0];
            
    String[] thelineSEC = lineSEC.split(" ");
    String fileNo2 = thelineSEC[0];
           
            if(fileNo1.equals(fileNo2))  
            {
               printWriter.println(lineFRST); 
            }
            else
            {  
            	printWriter.println(lineFRST); 
            	printWriter.println(lineSEC); 
            }
                    
            printWriter.close();
             
            lineFRST = in1.readLine(); 
            lineSEC = in1.readLine(); 
        }  
       
         in1.close();

Problem here is - Read from one file, read 2 lines one short, compare then move them to next two lines...I will miss some equal lines if keep moving two lines one short...again kindly teach me...thank you

Is this possible to achieve?

[prometheuzz]

Is this possible to achieve?

Of course it is, but how you're trying to do it, is not the best way to do so.
IMO it's better to first read all the lines from your textfile in an array, and the analyse that array afterwards. Don't do these two things at the same time: a method should only be responsible for one thing!
Here's some pseudo code fo you to work on:
[CODE=java]import java.io.*;
import java.util.*;

public class Main {

private static void analyseLines(St ring[] lines) {
LOOP from 'i' <- 0 to 'lines.length'-1, each iteration increase 'i' by 2
String 'current' <- the first part of the element at 'lines[i]'
String 'next' <- the first part of the element at 'lines[i+1]'
IF 'current' is the same as 'next'
print 'lines[i]'
ELSE
print both 'lines[i]' and 'lines[i+1]'
END IF
END LOOP
}

private static String[] readLines(Strin g fileName) throws IOException {
List lines <- new dynamical list
// see: http://java.sun.com/j2se/1.4.2/docs/api/java/util/List.html

WHILE 'fileNames' has more lines
lines.add(line from 'fileNames')
END WHILE
return 'lines' as an array of Strings
}

public static void main(String[] args) throws IOException {
String[] lines = readLines("/path/to/your/textfile");
analyseLines(li nes);
}
}[/CODE]
Good luck.

[shana07]

Of course it is, but how you're trying to do it, is not the best way to do so.
IMO it's better to first read all the lines from your textfile in an array, and the analyse that array afterwards. Don't do these two things at the same time: a method should only be responsible for one thing!
Here's some pseudo code fo you to work on:
[CODE=java]import java.io.*;
import java.util.*;

public class Main {

private static void analyseLines(St ring[] lines) {
LOOP from 'i' <- 0 to 'lines.length'-1, each iteration increase 'i' by 2
String 'current' <- the first part of the element at 'lines[i]'
String 'next' <- the first part of the element at 'lines[i+1]'
IF 'current' is the same as 'next'
print 'lines[i]'
ELSE
print both 'lines[i]' and 'lines[i+1]'
END IF
END LOOP
}

private static String[] readLines(Strin g fileName) throws IOException {
List lines <- new dynamical list
// see: http://java.sun.com/j2se/1.4.2/docs/api/java/util/List.html

WHILE 'fileNames' has more lines
lines.add(line from 'fileNames')
END WHILE
return 'lines' as an array of Strings
}

public static void main(String[] args) throws IOException {
String[] lines = readLines("/path/to/your/textfile");
analyseLines(li nes);
}
}[/CODE]
Good luck.

Could you please take a look at my code? There are 3 errors still:

public class FinalSort
{  
     private static void analyseLines(String[] lines, int m)
     {
        PrintWriter printWriter = null;    
        BufferedWriter bufferWriter = null;
     
  printWriter = new PrintWriter(new BufferedWriter(new FileWriter("C:\\result\\" + m +"Final.txt", true)));   //To get back 40 output files: eg: 1Final.txt       
     	
     	for (int i=0; i < lines.length-1; i+=2)  {     	
             String pos = lines[0];
             String[] current = pos[i];     //array required but string found        
             String[] next = pos[i+1];   //array required but string found        
     		
     		if(current.equals(next)) {     	
     printWriter.println (lines[i]);    }		     		
     		else {
     		    printWriter.println (lines[i]);  
 		    printWriter.println (lines[i+1]); 
 }	
     	}     	
          }
     
     
     private static String[] readLines (String fileName) throws IOException
     {
     	List lines = new ArrayList();
     	
     	while (fileName != null)
     	{
     		lines.add (fileName); 
     	}     	
     	return lines;  //How to return 'lines' as an array of Strings?
     }
     
 
     public static void main(String[] args) throws IOException
    {        
     for (int m=1; m<=40; m++)  // there are 40 files need to be analysed - eg: 1ResultFile.txt
 {                        
               String[] lines = readLines (m + "ResultFile.txt");     
               analyseLines (lines, m);   
         }         
    }

}

[prometheuzz]

First get your readLines method working. Only then (try to) implement the analyseLines(.. .) method.

...
     private static String[] readLines (String fileName) throws IOException
     {
         List lines = new ArrayList();
         
         while (fileName != null)
         {
             lines.add (fileName); 
         }         
 ...

This is not how you read the lines of a text file. You managed to read lines from a textfile before haven't you?

...
         return lines;  //How to return 'lines' as an array of Strings?
     }

Have a look at the API docs of the List class I posted earlier. There is a method in there that does just that.

[shana07]

First get your readLines method working. Only then (try to) implement the analyseLines(.. .) method.




This is not how you read the lines of a text file. You managed to read lines from a textfile before haven't you?




Have a look at the API docs of the List class I posted earlier. There is a method in there that does just that.

Thank you..
Why it's giving error - can't find method toArray(java.ut il.list)?

private static String[] readLines (String fileName, int m) throws IOException
     {
     	List lines = new ArrayList();
        
        String lineFRST = "";
        String lineSEC = "";
        
  BufferedReader in1 = new BufferedReader (new FileReader( m + "FileInput.txt")); 
       
        lineFRST = in1.readLine(); 
        lineSEC = in1.readLine();   
       
     	while (fileName != null)
     	{
               lines.add (lineFRST); 
                lines.add(lineSEC);
     	}
     	
     	return toArray (lines);       //is this correct?
     }

[prometheuzz]

Thank you..
Why it's giving error - can't find method toArray(java.ut il.list)?

....

return toArray (lines); //is this correct?
}[/CODE]

Because there is no method called toArray(...) in your class. You should call that method on your 'lines' reference.

...

private static String[] readLines (String fileName, int m) throws IOException
     {
     	List lines = new ArrayList();
        
        String lineFRST = "";
        String lineSEC = "";
        
  BufferedReader in1 = new BufferedReader (new FileReader( m + "FileInput.txt")); 
       
        lineFRST = in1.readLine(); 
        lineSEC = in1.readLine();   
       
     	while (fileName != null)
     	{
               lines.add (lineFRST); 
                lines.add(lineSEC);
     	}
	...
     }

No: do NOT read two lines at a time. Just read one at a time and add that one line in your List.

[shana07]

Because there is no method called toArray(...) in your class. You should call that method on your 'lines' reference.




No: do NOT read two lines at a time. Just read one at a time and add that one line in your List.

private static String[] readLines (String fileName, int m) throws IOException
     {
     	List lines = new ArrayList();
        
     	String lineFRST = "";
        String lineSEC = "";
        
        BufferedReader in1 = new BufferedReader (new FileReader( m + "FileInput.txt")); 
       
        lineFRST = in1.readLine();        //Okay?
       
     	while (fileName != null)
     	{
     		lines.add (lineFRST);                
     	}
     	
     	return (String[]) lines.toArray();   //Okay?           
     }

Please teach me what's next...TQ

[prometheuzz]

private static String[] readLines (String fileName, int m) throws IOException
     {
     	List lines = new ArrayList();
        
     	String lineFRST = "";
        String lineSEC = "";
        
        BufferedReader in1 = new BufferedReader (new FileReader( m + "FileInput.txt")); 
       
        lineFRST = in1.readLine();        //Okay?
       
     	while (fileName != null)
     	{
     		lines.add (lineFRST);                
     	}
     	
     	return (String[]) lines.toArray();   //Okay?           
     }

Please teach me what's next...TQ

Whether it OK or not can be easily asked to your compiler.
First check if your readLines(...) method works by printing the array your method returns like this:
[CODE=java]import java.io.*;
import java.util.*;

public class Main {

private static String[] readLines(Strin g fileName, int m) throws IOException {
List lines = new ArrayList();
String lineFRST = "";
BufferedReader in1 = new BufferedReader( new FileReader(m+"F ileInput.txt")) ;
lineFRST = in1.readLine();
while(fileName != null) {
lines.add(lineF RST);
}
return (String[])lines.toArray( );
}

public static void main(String[] args) throws IOException {
String[] lines = readLines("/path/to/your/textfile", 1);
for(int i = 0; i < lines.length; i++) {
System.out.prin tln("lines["+i+"] = "+lines[i]);
}
}
}[/CODE]

[shana07]

Whether it OK or not can be easily asked to your compiler.
First check if your readLines(...) method works by printing the array your method returns like this:
[CODE=java]import java.io.*;
import java.util.*;

public class Main {

private static String[] readLines(Strin g fileName, int m) throws IOException {
List lines = new ArrayList();
String lineFRST = "";
BufferedReader in1 = new BufferedReader( new FileReader(m+"F ileInput.txt")) ;
lineFRST = in1.readLine();
while(fileName != null) {
lines.add(lineF RST);
}
return (String[])lines.toArray( );
}

public static void main(String[] args) throws IOException {
String[] lines = readLines("/path/to/your/textfile", 1);
for(int i = 0; i < lines.length; i++) {
System.out.prin tln("lines["+i+"] = "+lines[i]);
}
}
}[/CODE]

Opss...you're right.
Exception in thread " main" java.lang.OutOf MemoryError: Java heap space...
What am I supposed to do then yeah.