Compare text files

[Monish Chandrasekar]

Hi,

Im trying to compare two text files in java, I wanted the source file and target file to be displayed side by side and the line which is different needs to be highlighted

I tried with this code, But it only shows the difference, what will I need to change to display two files side by side Like in http://www.comparemyfiles.com/

	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub

		//Compare c=new Compare();
		//List<String> s=c.FileCompare("D:/reference.xml", "D:/comparison.xml");
		
		
				//Getting the name of the files to be compared.
				BufferedReader br2 = new BufferedReader (new
				InputStreamReader(System.in));
				System.out.println("Enter 1st File name:");
		  		String str = br2.readLine();
		  		System.out.println("Enter 2nd File name:");
		  		String str1 = br2.readLine();

				String s1="";
		  		String s2="",s3="",s4="";
		  		String y="",z="";

		        //Reading the contents of the files
		 		BufferedReader br = new BufferedReader (new FileReader (str));
		  		BufferedReader br1 = new BufferedReader (new FileReader (str1));

		 		while((z=br1.readLine())!=null){
		 			s3+=z;
		 			System.out.println(z);
		 		}

				while((y=br.readLine())!=null)
		  			s1+=y;

				System.out.println ();

		        //String tokenizing
		  		int numTokens = 0;
		  		StringTokenizer st = new StringTokenizer (s1);
		  		String[] a = new String[10000];
		  		for(int l=0;l<10000;l++)
			   		{a[l]="";}
		  		int i=0;
		  		while (st.hasMoreTokens())
		    	 {
		      		s2 = st.nextToken();
		     	    a[i]=s2;
					i++;
		            numTokens++;
		    	 }

		     	int numTokens1 = 0;
			   	StringTokenizer st1 = new StringTokenizer (s3);
			   	String[] b = new String[10000];
			   	for(int k=0;k<10000;k++)
			   		{b[k]="";}
			   	int j=0;
			   	while (st1.hasMoreTokens())
			      {
			       s4 = st1.nextToken();
			       b[j]=s4;
			       j++;
			       numTokens1++;
			      }

		//comparing the contents of the files and printing the differences, if any.
				int x=0;
		     	for(int m=0;m<a.length;m++)
		     	{
					if(a[m].equals(b[m])){}
				 	else
				 	{
				 		x++;
				System.out.println(a[m] + " -- " +b[m]);
				System.out.println();}
				    }
		 System.out.println("No. of differences : " + x);
		 if(x>0){System.out.println("Files are not equal");}
		 else{System.out.println("Files are equal. No difference found");}

	}

}

[Tony Docherty]

If you want to do it like the link you'll need a GUI.
If you want to keep it as CLI, print out the files side by side with some marker to show lines that don't match then add a print statement to the if statement that compares the lines for equality. You will need to change the chars you insert between the two concatenated lines so you can see which lines are not the same.

[Campbell Ritchie]

And welcome to the Ranch

[Ulf Dittmer]

If you want to minimize your work, use Runtime.exec to run "diff" on the two files and do something with its output (You'd need Unix/Linux underneath, or UnxUtils installed on Windows, though.)

Or check out http://jlibdiff.sourceforge.net/ and http://code.google.com/p/google-diff-match-patch/

[Campbell Ritchie]

Don’t use StringTokenizer (← click here and it tells you why).
Don’t use a 10000 element array. The alternatives to tokenizer can produce an array of the right size.