java: pass-by-value or pass-by-reference

I'd two code
snippets:

First

class
            PassByTest{
 public static void main(String... args){
 PassByTest
            pbt=new PassByTest();
 int x=10;
 System.out.println("x=
            "+x);
 pbt.incr(x);//x is passed for increment

            System.out.println("x= "+x);//x is unaffected
 }
 public void
            incr(int x){
 x+=1;

            }
}

In this code the
value of x is
unaffected.

Second

import
            java.io.*;
class PassByteTest{
 public static void
            main(String...args) throws IOException{
 FileInputStream fis=new
            FileInputStream(args[0]);
 byte[] b=new byte[fis.available()];

            fis.read(b);//how all the content is available in this byte[]?
 for(int
            i=0;i System.out.print((char)b[i]+"");

            if(b[i]==32)
 System.out.println();
 }

            }
}

In this all the
content of file is available in the byte[] b.
How
and Why?