Convert boolean, int

A Java boolean is true or false. But often when developing a program we want the integer 1 or 0 to represent truth. We must convert a boolean to an int.

A problem

We cannot cast a boolean to an int in Java. We must use an if-statement, or a ternary, to convert. A separate method can be used to encapsulate and name this logic.

Example method

Here we introduce a method booleanToInt. We use a ternary expression to convert the boolean to 1 or 0. If true, we return 1. If false, we return the value 0.

public class Program {

    public static int booleanToInt(boolean value) {
        // Convert true to 1 and false to 0.
        return value ? 1 : 0;
    }

    public static void main(String[] args) {
        // Test our conversion method.
        boolean value = false;
        int number = booleanToInt(value);
        System.out.println(number);
        System.out.println(booleanToInt(true));
    }
}
0
1

Error, cast boolean

This program does not work. It does not compile. It attempts to cast a boolean to an int. This is not possible in Java—it cannot be done.

public class Program {

    public static void main(String[] args) {
        // This does not compile.
        boolean value = true;
        int value2 = (int) value;
    }
}
Exception in thread "main" java.lang.Error:
    Unresolved compilation problem:
    Cannot cast from boolean to int
    at Program.main(Program.java:6)

Performance notes

The booleanToInt method requires a branch in its implementation. This is not as fast as simply using 0 and 1 to represent truth.

What we accomplished

We found that there is no way to directly cast a boolean to an int in Java. This causes an error. Instead we can use a ternary to evaluate and return an int.