**Java Tutorials - Herong's Tutorial Examples** - Version 7.01, by Dr. Herong Yang

Shift Operations - Left, Right or Unsigned Right Shift

This section describes shift operations: 'Left Shift', 'Right Shift', and 'Unsigned Right Shift'. A tutorial example is provided to show you how shift operations work on 'int' data type values.

What is a shift operation? A shift operation is an operation that requires the operand to be represented in a binary format, viewed as a bit string, then shift all bit values to the left or right.

Again, Java defines shift operations on "int" data type values, not on "byte" data type values. So a shift operation requires that the involved "int" value to be represented into a bit string of 32 bits. And the operation will be applied to shift bit values to the left or right on the bit string.

Java defines 3 shift operations called: "Left Shift", "Right Shift", and "Unsigned Right Shift":

1. Shift operation "Left Shift" - "<<": The "Left Shift" operation on an "int" value can be described as:

- Representing the first operand, an "int" values, into a bit string of 32 bits.
- Shift all bit values to the left and fill the empty bits on the right end with a 0 value. The number of bits to shift is given in the second operand.
- Converting the shifted bit string to an "int" value as the operation result.

The following diagram gives an example of a "<<" operation in 2 formats:

Decimal Binary -858993460 << 6 11001100110011001100110011001100 << 6 ----------------- --------------------------------------- = 858993408 = 00110011001100110011001100000000

2. Shift operation "Right Shift" - ">>": The "Right Shift" operation on an "int" value can be described as:

- Representing the first operand, an "int" values, into a bit string of 32 bits.
- Shift all bit values to the right and fill the empty bits on the left end with the original value of the sign bit, the most left bit of the bit string. The number of bits to shift is given in the second operand.
- Converting the shifted bit string to an "int" value as the operation result.

The following diagram gives an example of a ">>" operation in 2 formats:

Decimal Binary -858993460 >> 6 11001100110011001100110011001100 >> 6 ----------------- --------------------------------------- =4281545523 = 11111111001100110011001100110011

3. Shift operation "Unsigned Right Shift" - ">>>": The "Unsigned Right Shift" operation on an "int" value can be described as:

- Representing the first operand, an "int" values, into a bit string of 32 bits.
- Shift all bit values to the right and fill the empty bits on the left end with a 0 value The number of bits to shift is given in the second operand.
- Converting the shifted bit string to an "int" value as the operation result.

The following diagram gives an example of a ">>>" operation in 2 formats:

Decimal Binary -858993460 >>> 6 11001100110011001100110011001100 >>> 6 ----------------- --------------------------------------- = 53687091 = 00000011001100110011001100110011

To verify the examples given above, I wrote the following test program, ShiftOperations.java:

/* ShiftOperations.java - Copyright (c) 2014, HerongYang.com, All Rights Reserved. */ public class ShiftOperations { public static void main(String[] arg) { int a = -858993460; // binary: 11001100110011001100110011001100 int o1 = a << 6; // left shift int o2 = a >> 6; // right shift int o3 = a >>> 6; // unsigned right shift System.out.println(" a: "+getBitString(a) +" = "+a); System.out.println("o1: "+getBitString(o1) +" = "+o1); System.out.println("o2: "+getBitString(o2) +" = "+o2); System.out.println("o3: "+getBitString(o3) +" = "+o3); } private static String getBitString(int x) { StringBuffer buf = new StringBuffer(); for (int i=1; i<=32; i++) buf.append(x>>>(32-i) & 0x00000001); return buf.toString(); } }

The output of the test program matches my earlier examples:

a: 11001100110011001100110011001100 = -858993460 o1: 00110011001100110011001100000000 = 858993408 o2: 11111111001100110011001100110011 = -13421773 o3: 00000011001100110011001100110011 = 53687091

*Last update: 2014.*

Table of Contents

Execution Process, Entry Point, Input and Output

Primitive Data Types and Literals

►Bits, Bytes, Bitwise and Shift Operations

"byte" Data Type and Implicit Casting

Operations on "byte" Data Type Values

Bitwise Operations on "byte" Values

Bitwise Operations on "byte" Values - Example Program

►Shift Operations - Left, Right or Unsigned Right Shift

Managing Bit Strings in Byte Arrays

Reference Data Types and Variables

StringBuffer - The String Buffer Class

System Properties and Runtime Object Methods

Generic Classes and Parameterized Types

Generic Methods and Type Inference

Lambda Expressions and Method References

Execution Threads and Multi-Threading Java Programs

ThreadGroup Class and "system" ThreadGroup Tree

Synchronization Technique and Synchronized Code Blocks

Deadlock Condition Example Programs