boolean

A boolean is a primitive data type in Java that can hold only two values:

• true
• false

Booleans are mainly used to:

• Make decisions in programs (e.g. if something is true, do one thing; otherwise do something else)
• Track states (e.g. is a user logged in? is a light switched on?)

Declaring a boolean

You create a boolean using the boolean keyword:

boolean isActive = true;
boolean isLoggedIn = false;

Primitive type

A boolean is a primitive type. It stores its value directly in memory, rather than storing a reference to an object. When you change a boolean’s value, the old value is simply replaced:

boolean isActive = true;
System.out.println(isActive); // true

isActive = false;
System.out.println(isActive); // false

Long wrapper class

Even though boolean is a primitive type, there is a corresponding wrapper class called Boolean (with a capital B). This class provides useful methods to work with boolean values. Below are some common methods

Conversion methods

Convert primitive boolean to Boolean object

boolean b = true;
Boolean obj = Boolean.valueOf(b);

Convert String to Boolean object

String s = "true";
Boolean obj = Boolean.valueOf(s); // case insensitive

Convert String to primitive boolean

String s = "true";
boolean b = Boolean.parseBoolean(s); // returns true or false. Case insensitive

Convert primitive boolean to String

boolean b = true;
String s = Boolean.toString(b);

Convert Boolean object to String

Boolean b = Boolean.TRUE;
String s = b.toString(); // returns "true"

Comparison methods

compare

Boolean.compare(true, false)

compareTo

Boolean b1 = true;
Boolean b2 = false;

b1.equals(b2); // false

Both compare and compareTo return these values:

• 0 → if values are equal
• -1 → if first is less than second
• 1 → first is greater than second

equals

Boolean b1 = true;
Boolean b2 = false;

b1.equals(b2); // false
// returns true if both values are equal, else returns false

Summary

• boolean stores true or false
• boolean is used for decisions and states
• boolean is a primitive type with no methods
• Boolean is the wrapper class that gives the boolean primitive access to methods

Further Reading

• Java Boolean class
• Java primitives