The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
The equality and relational operators determine if one operand is greater than, less than, equal to, or not equal to another operand. The majority of these operators will probably look familiar to you as well. Keep in mind that you must use "==
", not "=
", when testing if two primitive values are equal.
== equal to != not equal to > greater than >= greater than or equal to < less than <= less than or equal to
The following program,
ComparisonDemo
, tests the comparison operators:
class ComparisonDemo { public static void main(String[] args){ int value1 = 1; int value2 = 2; if(value1 == value2) System.out.println("value1 == value2"); if(value1 != value2) System.out.println("value1 != value2"); if(value1 > value2) System.out.println("value1 > value2"); if(value1 < value2) System.out.println("value1 < value2"); if(value1 <= value2) System.out.println("value1 <= value2"); } }
Output:
value1 != value2 value1 < value2 value1 <= value2
The &&
and ||
operators perform Conditional-AND and Conditional-OR operations on two boolean expressions. These operators exhibit "short-circuiting" behavior, which means that the second operand is evaluated only if needed.
&& Conditional-AND || Conditional-OR
The following program,
ConditionalDemo1
, tests these operators:
class ConditionalDemo1 { public static void main(String[] args){ int value1 = 1; int value2 = 2; if((value1 == 1) && (value2 == 2)) System.out.println("value1 is 1 AND value2 is 2"); if((value1 == 1) || (value2 == 1)) System.out.println("value1 is 1 OR value2 is 1"); } }
Another conditional operator is ?:
, which can be thought of as shorthand for an if-then-else
statement (discussed in the
Control Flow Statements section of this lesson). This operator is also known as the ternary operator because it uses three operands. In the following example, this operator should be read as: "If someCondition
is true
, assign the value of value1
to result
. Otherwise, assign the value of value2
to result
."
The following program,
ConditionalDemo2
, tests the ?:
operator:
class ConditionalDemo2 { public static void main(String[] args){ int value1 = 1; int value2 = 2; int result; boolean someCondition = true; result = someCondition ? value1 : value2; System.out.println(result); } }
Because someCondition
is true, this program prints "1" to the screen. Use the ?:
operator instead of an if-then-else
statement if it makes your code more readable; for example, when the expressions are compact and without side-effects (such as assignments).
The instanceof
operator compares an object to a specified type. You can use it to test if an object is an instance of a class, an instance of a subclass, or an instance of a class that implements a particular interface.
The following program,
InstanceofDemo
, defines a parent class (named Parent
), a simple interface (named MyInterface
), and a child class (named Child
) that inherits from the parent and implements the interface.
class InstanceofDemo { public static void main(String[] args) { Parent obj1 = new Parent(); Parent obj2 = new Child(); System.out.println("obj1 instanceof Parent: " + (obj1 instanceof Parent)); System.out.println("obj1 instanceof Child: " + (obj1 instanceof Child)); System.out.println("obj1 instanceof MyInterface: " + (obj1 instanceof MyInterface)); System.out.println("obj2 instanceof Parent: " + (obj2 instanceof Parent)); System.out.println("obj2 instanceof Child: " + (obj2 instanceof Child)); System.out.println("obj2 instanceof MyInterface: " + (obj2 instanceof MyInterface)); } } class Parent {} class Child extends Parent implements MyInterface {} interface MyInterface {}
Output:
obj1 instanceof Parent: true obj1 instanceof Child: false obj1 instanceof MyInterface: false obj2 instanceof Parent: true obj2 instanceof Child: true obj2 instanceof MyInterface: true
When using the instanceof
operator, keep in mind that null
is not an instance of anything.