Secret in java

First look at the code:
Integer i=new Integer(5);
integer j=10;
here what happening two object is created of integer type whose value type is int
Integer value lies between -2147483648 to 2147483647
ok fine...

Integer i=127;
Integer j=127;
here what happen one object is created pointed by two referece i and j
lets see..
if(i==j)
{System.out.println("yes");}
else
{System.out.println("no");}

here o/p we get yes
Now once again.......

Integer a=128;
Integer b=128;
here what happen two object is created one pointed by  referece a and another pointing by reference b
lets see..
if(a==b)
{System.out.println("yes");}
else{System.out.println("no");}

here o/p we get no

How it happen...?????

Initially I too get shocked , how it happen?,i opened the book, surf the site then i came to the conclusion....
Bydefault jvm have limited heap memory which we can increase manually......
because of this bydefault limited heap memory Integers between -127 and 127 are 'cached' in such a way
that when you use those numbers you always refer to the same number in memory, which is why your == works.
In simple we can say that Integer value can be consider as three type

Data Type            Value                            Memory
byte            -128 -- +127                    occupy 1 byte (8 bits) in memory
short            -32768 -- 32767             occupy 2 bytes (16 bits) in memory
int            -2147483648 -- 2147483647   occupy 4 bytes (32 bits) in memory


and for least data type i.e byte value is cached in such a way that when you use those numbers you always refer to the same number in memory,because of limit heap memory
 

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Check at what techniques your OS is working through Java.

There are two major types of scheduling techniques in the modern operating systems: round-robin and time-slicing.Now how can you identify at what techniques your OS is working through Java.

class Thready {
public static void main( String args [] ) {
new MyThread("A").start();
new MyThread("B").start();
}
}

class MyThread extends Thread {
String message;

MyThread ( String message ) {
this.message = message;
}

public void run() {
while ( true )
System.out.print( message );
}
}
if you get O/P:
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBBBBBBBAAAAAAAAAAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBBBBBB

then your OS is using Round Robin,The output is generated by an implementation of Java virtual machine for a preemptive system like UNIX OSF1, Windows 95, Windows NT, etc,

if your O/P is:
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA...........

then it using time-slicing ,the output is generated by an implementation of Java virtual machine for a non-preemptive system based on Solaris UNIX platforms

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