Java Converting Between Binary, Octal, Decimal, and Hexadecimal

Java Converting Between Binary, Octal, Decimal,

and Hexadecimal

Problem

You want to display an integer as a series of bits—for example, when interacting
with certain hardware devices. You want to convert a binary number or a hexadecimal value into an integer.

Solution

The class java.lang.Integer provides the solutions. Use toBinaryString( ) to con-
vert an integer to binary. Use valueOf( ) to convert a binary string to an integer:

// BinaryDigits.java
String bin = "101010";
System.out.println(bin + " as an integer is " + Integer.valueOf(bin, 2));
int i = 42;
System.out.println(i + " as binary digits (bits) is " +
Integer.toBinaryString(i));

This program prints the binary as an integer, and an integer as binary:

$ java BinaryDigits
101010 as an integer is 42
42 as binary digits (bits) is 101010
$

Explained

Integer.valueOf( ) is more general than binary formatting. It also converts a string number from any radix to int , just by changing the second argument. Octal is base 8, decimal is 10, hexadecimal 16. Going the other way, the Integer class includes toBinaryString( ) , toOctalString( ) , and toHexString( ) . The String class itself includes a series of static methods, valueOf(int) , valueOf(double) , and so on, that also provide default formatting. That is, they return the given numeric value formatted as a string.