Left shift and right shift operators in Java

Left shift and right shift operators in Java

A lot of time we use >> , >>> or << and <<< operators in Java for bit operations. These operations essentially shift bits left or right depending on the operator. In this post we will see what exactly is the difference.

• >> is arithmetic or signed shift right
• >>> is logical or unsigned shift right
• << is arithmetic or signed shift left

The signed left shift operator "<<" shifts a bit pattern to the left, and the signed right shift operator ">>" shifts a bit pattern to the right. The bit pattern is given by the left-hand operand, and the number of positions to shift by the right-hand operand.

The unsigned right shift operator ">>>" shifts a zero into the leftmost position, while the leftmost position after ">>" depends on sign extension.

NOTE : There is no logic left shift as it is same as arithmetic left shift.

Example :

        System.out.println(Integer.toBinaryString(-121));
        // prints "11111111111111111111111110000111"
        System.out.println(Integer.toBinaryString(-121 >> 1));
        // prints "11111111111111111111111111000011"
        System.out.println(Integer.toBinaryString(-121 >>> 1));
        // prints "1111111111111111111111111000011"
        
        System.out.println(Integer.toBinaryString(121));
        // prints "1111001"
        System.out.println(Integer.toBinaryString(121 >> 1));
        // prints "111100"
        System.out.println(Integer.toBinaryString(121 >>> 1));
        // prints "111100"

As you can see in case of -121 since it is a negative number arithmetic or signed shift right adds a 1 to the rightmost bit where as in case if 121 it adds 0.

logical or unsigned shift does not care about sign. It just adds 0 to the shifted bits.

Related Links

• Java documentation
• How ConcurrentHashMap Works Internally in Java(OSFG)