Operators in Java Cont..

Java Logical Operators

 Sometimes, whether a statement is executed is determined by a combination of several conditions.You can use logical operators to combine these conditions. Logical operators are known as Boolean operators or bitwise logical operators. Boolean operator operates on boolean values to create a new boolean value.The bitwise logical operators are “&”, “|”, “^”, and “~” or “!”. The following table shows the outcome ofeach operation.

a	b	a&b	a|b	a^b	~a or !a
true(1)	true(1)	TRUE	TRUE	FALSE	FALSE
true(1)	false(0)	FALSE	TRUE	TRUE	FALSE
false(0)	true(1)	FALSE	TRUE	TRUE	TRUE
false(0)	false(0)	FALSE	FALSE	FALSE	TRUE

The NOT Operator

Also called the bitwise complement, the unary NOT operator, ~, inverts all of the bits of its operand. If applied on integer operand it will reverse all bits similarly if applied to boolean literal it will reverse it.

int a =23; // 23 is represented in binary as 10111

int b = ~a; // this will reverts the bits 01000 which is 8 in decimal

boolean x = true;

boolean y = !x;  // This will assign false value to y as x is true

The AND Operator

The AND operator “&” produces a 1 bit if both operands are 1 otherwise 0 bit. Similarly for boolean operands it will result in true if both operands are true else result will be false.

 int var1 = 23; //boolean value would be 010111

int var2 = 33; //boolean value would be 100001

int var3=var1 & var2 // result in binary 000001 & in decimal 1

boolean b1 = true;

boolean b2=false;

boolean b3 = b1&b2; // b3 would be false

The OR Operator

The OR operator “|” produces a 0 bit if both operands are 0 otherwise 1 bit. Similarly for boolean operands it will result in false if both operands are false else result will be true.

int var1 = 23; //boolean value would be 010111

int var2 = 33; //boolean value would be 100001

int var3=var1 | var2 // result in binary 110111& in decimal 55

boolean b1 = true;

boolean b2=false;

booleanb3 = b1|b2; // b3 would be true

The XOR (exclusive OR) Operator

The XOR operator “^” produces a 0 bit if both operands are same (either both 0 or both 1) otherwise 1 bit. Similarly for boolean operands it will result in false if both operands are same (either both are false or both true) else result will be true.

int var1 = 23; //boolean value would be 010111

int var2 = 33; //boolean value would be 100001

int var3=var1 ^ var2 // result in binary 110110& in decimal 54

boolean b1 = true;

boolean b2=false;

booleanb3 = b1 ^ b2; // b3 would be true

Let’s look at below program which demonstrate above operators for boolean and integer operation.

public class BitwiseLogicalOpDemo
{ 
    public static void main(String[] args)
    { 
        //Integer bitwise logical operator 
        int a = 65; // binary representation 1000001 
        int b = 33; // binary representation 0100001 
        System.out.println("a & b= " + (a & b)); 
        System.out.println("a | b= " + (a | b)); 
        System.out.println("a ^ b= " + (a ^ b)); 
        System.out.println("~a= " + ~a); 
        //boolean logical operator 
        boolean bool1 = true; 
        boolean bool2 = true; 
        boolean bool3 = false; 
        System.out.println("bool1 & bool2= " + (bool1 & bool2)); 
        System.out.println("bool2 & bool3= " + (bool2 | bool3)); 
        System.out.println("bool2 | bool3= " + (bool2 | bool3)); 
        System.out.println("bool1 ^ bool2= " + (bool1 ^ bool2));
        System.out.println("!bool1= " + !bool1);
    }
} 

Bitwise Shift Operators:

>> (Signed right shift):

In Java, the operator “>>” is signed right shift operator. All integers are signed in Java, and it is fine to use >> for negative numbers. The operator “>>” uses the sign bit (left most bit) to fill the trailing positions after shift. If the number is negative, then 1 is used as a filler and if the number is positive, then 0 is used as a filler. In simple terms it will divide the number by 2 to power number of shifted bit

int a =8; //binary representation is 1000

System.out.println(a>>1); //This will print 4 (binary representation 0100)

<< (Singed left shift):

This operator moves all bits to left side (simply multiply the number by two to power number of bits shifted).

int a =8; //binary representation is 1000

System.out.println(a<<2); //This will print 32 (binary representation 100000) 

>>> (Unsigned right shift) :

As you have just seen, the >> operator automatically fills the high-order bit with its previous contents each time a shift occurs. This preserves the sign of the value. However, sometimes this is undesirable. For example, if you are shifting something that does not represent a numeric value, you may not want sign extension to take place. First bit represent sign of integer.

 int a =-2; // This is represented in binary as 10000000 0000000000000000 000000010

System.out.println(a>>>1);

//01000000 00000000 00000000 00000001 in decimal=2147483647

 Below program demonstrate shift operators.

public class ShiftOperatorDemo
{
    public static void main(String[] args)
    {
        int a = 34;  //binary representation 00000000 00000000 00000000 00100010 
        int b = -20; //binary representation 10000000 00000000 00000000 00010100 
        System.out.println("Signed Right Shift 34 devide by 2= " + (a>>1) );
        System.out.println("Signed Right Shift -20 devide by 2= " + (b>>1) );
        System.out.println("Signed Left Shift 34 multiply by 2= " + (a<<1) );
        System.out.println("Signed Letf Shift -20 multiply by 2= " + (b<<1) );
        System.out.println("unsigned Right Shift of 34 = " + (a>>>1) );
        System.out.println("unsigned Right Shift of -20 = " + (b>>>1) );
    }
}   

Summary

• Logical operators are known as Boolean operators or bitwise logical operators.
• Logical operators are & (and), | (or), ^ (ex-or), !/~ (not).
• Binary Shift operators are >> (right shift), << (left shift), >>> (unsigned right shift).