Java HowTo Guide

The relational operators work well in conditions where only a single condition needs to be checked. Logical operators either return a True value or a False value based on the state of the Variables. The six logical or Boolean, operators used in the Java programming language are:

• AND
• conditional AND
• OR
• conditional OR
• exclusive OR
• NOT

A logical operator accepts only arguments declared as Boolean data types. Also, these operators return value of Boolean data type.

These operators unlike the relational operators, that you already know, are used to check whether a set of conditions is true or not. In such as case, if statements are used. The code snippet below shows example of this:

if (num_var_1 == 4) {

  if (num_var_2 != 4) {

     System.out.println("Both conditions are true.");

   }

}

However, as you can see this is not a user-friendly code, and is both harder to write and read. Such a code snippet becomes difficult to manage when multiple conditions are used. Let’s now look at the use of the following three conditional operators:&&, || and !.

The logical operator && combines two Boolean values and gives a True result if and only if both of its operands are true. This is shown in the following code snippet:

Boolean c;

num_var_1 = 51 > 49 && 13 < 13; // num_var_1 is true

num_var_1 = 44 > 52 && 7 < 9; // num_var_1 is now false

Similarly, the logical operator || combines two Boolean variables or expressions. It returns a true result only if either or both of its operands are true. Let’s look at the following code snippet which shows the rule:

Boolean d;

num_var_4 = 51 > 49 || 73 < 91; // num_var_4 is true

num_var_4 = 49 > 51 || 73 < 91; // num_var_4 is still true

num_var_4 = 49 > 51 || 73 > 91; // now num_var_4 is false

The third and the last logic operator which we will look at is “!”  Which denotes “not”. The “!” logical operator reverses the value of a Boolean expression.

According to this logical operator:

if x is true !x is false.

If x is false  !x is true.

boolean bol_var_1;

bol_var_1 = !(4 > 5); // bol_var_1 is false

bol_var_1 = !(5 > 4); // bol_var_1 is true

As already stated logical operators allow you to test and use multiple conditions. For example, we can use the logical operators in the code snippet we saw above as follows:

if (var_num_1 == 2 && var_num_2 != 2) {

  System.out.println("Both conditions are true.");

}

Let’s look at a code snippet Demo_of_Logical_Operators which makes use of multiple logical operators:

public class Demo_of_Logical_Operators

{

public Demo_of_Logical_Operators () {

boolean bol_var_1 = true;

boolean bol_var_2 = false;

System.out.println(“bol_var_1 & bol_var_2 : ” + (bol_var_1 & bol_var_2));

System.out.println(“bol_var_1 && bol_var_2 : ” + (bol_var_1 && bol_var_2));

System.out.println(“bol_var_1 | bol_var_2 : ” + (bol_var_1 | bol_var_2));

System.out.println(“bol_var_1 || bol_var_2: ” + (bol_var_1 || bol_var_2));

System.out.println(“bol_var_1 ^ bol_var_2 : ” + (bol_var_1 ^ bol_var_2));

System.out.println(“!bol_var_1 : ” + (!bol_var_1));

}

public static void main(String args[]) {

new Demo_of_Logical_Operators ();

The table given below defines the different Boolean operators, if x and y are both Boolean expressions.

x	y	!x	x & y x && y	x | y x || y	x ^ y
true	true	false	true	true	false
true	false	false	false	true	true
false	true	true	false	true	true
false	false	true	false	false	false