import java.io.File;
import java.io.FileInputStream;

import java.io.BufferedInputStream;

/**
*
* @author shyam

*/
public class Test {

/**
* @param args the command line arguments
*/
public static void main(String[] args) throws Exception{
String filePath1="c:/file1.txt";
String filePath2="c:/file2.txt";

Test test=new Test();

//Using FileInputStream
if(test.compareFiles(filePath1,filePath2)){
System.out.println("Both the files are same.");
}
else{
System.out.println("Files are not same.");
}

//Using BufferedInputStream on FileInputStream

if(test.compareFilesWithBuffer(filePath1,filePath2)){
System.out.println("Both the files are same.");
}
else{
System.out.println("Files are not same.");
}

 
}

 

//    A BufferedInputStream adds functionality to another input stream-namely,
//     the ability to buffer the input and to support the mark and reset methods.
//     When the BufferedInputStream is created, an internal buffer array is created.
//     As bytes from the stream are read or skipped, the internal buffer is refilled
//     as necessary from the contained input stream, many bytes at a time.
//     The mark operation remembers a point in the input stream and the reset
//     operation causes all the bytes read since the most recent mark operation
//     to be reread before new bytes are taken from the contained input stream.

boolean compareFilesWithBuffer(String filePath1,String filePath2){
        try{           
            File f1 = new File(filePath1);
            File f2 = new File(filePath2);
            if(f1.length() == f2.length()){
                BufferedInputStream bis1=new BufferedInputStream(new FileInputStream(f1));
                BufferedInputStream bis2=new BufferedInputStream(new FileInputStream(f2)); 

                while(true){
                    int a = bis1.read();
                    int b = bis2.read();
                    if(a != b){
                        return false;
                    }
                    if(a == -1){
                        return true;
                    }
                }
            }else{
                return false;
            }
        }catch(Exception e){
            e.printStackTrace();
        }
        return false;
    }

 

boolean compareFiles(String filePath1,String filePath2){
try{
File f1 = new File(filePath1);
File f2 = new File(filePath2);
if(f1.length() == f2.length()){
FileInputStream fis1 = new FileInputStream(f1);
FileInputStream fis2 = new FileInputStream(f2);

while(true){
int a = fis1.read();
int b = fis2.read();
if(a != b){
return false;
}
if(a == -1){
return true;
}
}
}else{
return false;
}

}catch(Exception e){
e.printStackTrace();
}
return false;
}
 
}