In Java, can I define an integer constant in binary format?

In Java 7:

int i = 0b10101010;

There are no binary literals in older versions of Java (see other answers for alternatives).

So, with the release of Java SE 7, binary notation comes standard out of the box. The syntax is quite straight forward and obvious if you have a decent understanding of binary:

byte fourTimesThree = 0b1100;byte data = 0b0000110011;short number = 0b111111111111111; int overflow = 0b10101010101010101010101010101011;long bow = 0b101010101010101010101010101010111L;

And specifically on the point of declaring class level variables as binaries, there's absolutely no problem initializing a static variable using binary notation either:

public static final int thingy = 0b0101;

Just be careful not to overflow the numbers with too much data, or else you'll get a compiler error:

byte data = 0b1100110011; // Type mismatch: cannot convert from int to byte

Now, if you really want to get fancy, you can combine that other neat new feature in Java 7 known as numeric literals with underscores. Take a look at these fancy examples of binary notation with literal underscores:

int overflow = 0b1010_1010_1010_1010_1010_1010_1010_1011;long bow = 0b1__01010101__01010101__01010101__01010111L;

Now isn't that nice and clean, not to mention highly readable?

I pulled these code snippets from a little article I wrote about the topic over at TheServerSide. Feel free to check it out for more details:

Java 7 and Binary Notation: Mastering the OCP Java Programmer (OCPJP) Exam

There are no binary literals in Java, but I suppose that you could do this (though I don't see the point):

int a = Integer.parseInt("10101010", 2);