The Equality and Relational OperatorsThe equality and relational operators determine if one operator 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.The following program,== equal to != not equal to > greater than >= greater than or equal to < less than <= less than or equal toComparisonDemo
, tests the comparison operators:Output: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"); } }value1 != value2 value1 < value2 value1 <= value2The Conditional Operators
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-ORThe 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 anif-then
statement (discussed in the Control Flow Statements section of this lesson). In the following example, this operator should be read as: "IfsomeCondition
istrue
, assign the value ofvalue1
toresult
. Otherwise, assign the value ofvalue2
toresult
."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 anif-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 Type Comparison Operator instanceof
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 (namedParent
), a simple interface (namedMyInterface
), and a child class (namedChild
) 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{}
When using theobj1 instanceof Parent: true obj1 instanceof Child: false obj1 instanceof MyInterface: false obj2 instanceof Parent: true obj2 instanceof Child: true obj2 instanceof MyInterface: trueinstanceof
operator, keep in mind is thatnull
is not an instance of anything.