Boolean Values

In Java, a Boolean value is one with two choices: true or false, yes or no, 1 or 0. Lets look at a few examples of booleans below:

boolean a = true;
boolean b = false;

Pretty simple, right? There are only two values for booleans, and they're true and false . However, there's a lot more to booleans than just these two values. There are a number of operators that can be applied to boolean values, which I'll explain below.

Boolean Unary Operators

Just like there is one unary operator for integers, there is one unary operator for boolean values: !. This operator basically flips the value of the boolean.

boolean a = true;
boolean b = false;
boolean c = !a;    // false
boolean d = !b;    // true

Boolean Binary Operators

There are 9 different binary operators for booleans: ==, !=, <, <=, >, >=, &&, ||, ^ . I will explain what they do below:

== : This operator checks if two boolean values are equal. Let's see how it works in the table below

!= : This operator is literally the opposite of the above operator. Let's look at the table below to see how it works:

< : This operator checks if the previous integer (or any numeric type) is strictly less than the integer after the operator. Lets check out a few examples:

boolean a = 2 < 3; // true
boolean b = 3 < 2; // false
boolean c = 3 < 3; // false

<= : This operator checks for less than or equal to. Lets check out a few examples:

boolean a = 2 <= 3; // true
boolean b = 3 <= 2; // false
boolean c = 3 <= 3; // true

Notice how the third boolean equates to true, because 3 is less than or equal to 3.

I won't be going over the > and >= operators (greater than and greater than or equal to), as they're self explanatory really.

&& : This operator takes two boolean values and checks if both of them are true. Let's look at the table below to see how it works:

Notice how this operator is similar to the bitwise and back in the binary operators for integers. That's because you can think of true and false as bits.

|| : This operator is basically the same as bitwise OR, lets see how below:

^ : This operator is basically the same as bitwise XOR. See below:

Note: this seems like it's equivalent to != , but for boolean values you should use != as it's much clearer. However, be prepared for either use in the actual event.

Exercises

1. What is the result of true == false ?
2. What is the result of false != false ?
3. What is the result of false || true ?
4. What is the result of true ^ false ?
5. What is the result of false && false ?
6. What is the result of 9 >= 8 ?
7. What is the result of 2 < 5 ?
8. What is the result of 7 <= 7 ?
9. What is the result of 8 > 4 ?

Boolean Ternary Operators

If you don't know what a ternary operator is, it is an operator that takes three values and produces one result. In java, the only ternary operator for boolean values is in the format a ? b : c . The way this works is if a is true, then the operator will return b, otherwise it'll return c . Keep in mind that the values b and c don't necessarily have to be boolean values and the purpose of ternary operators is to choose between two values of the same type. Lets look at a few values below:

int a = true ? 1 : 2;             // 1
char b = false ? 'x' : 'y';       // 'y'
boolean c = false ? true : false; // false;

Exercises

1. What is the result of true ? 7 : 6 ?
2. What is the result of false ? 'a' : 'b' ?
3. What is the result of false ? false : true ?
4. What is the result of true ? false : true ?
5. What is the result of false ? 0 : 1 ?
6. What is the result of true ? 35 : 53 ?