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Last Minute Java Boolean Logical Operators and Priority Tutorial

Java Boolean Logical Operators Priority

As the name suggests, Java Boolean Logical Operators work with boolean data type values. Some logical operators work with a single Operand while others work with two Operands. There are bitwise logical operators too which we discuss later.

Java Boolean Logical Operators with Priority

The list of Boolean Logical operators is given below. Note that the Logical Unary NOT (!) has got the highest priority among all other logical operators. The assignment operator has the least priority.

Note 1: Except for Logical NOT(!), all other logical operators have less priority than Arithmetic and Relational operators.

Boolean Logical Operators with Priority
Priority Operator Simple Name
1 ! Logical Unary NOT
2 & Logical AND
3 ^ Exclusive OR or XOR
4 | Logical OR
5 && Logical Short Circuit AND
6 || Logical Short Circuit OR
7 op=

Compound Assignment Operator

&=, |=, ^=

7 = Assignment

Note 2: Generally, software programmers use only Short Circuit Logical operators compared to normal logical operators for good performance and to differentiate bitwise AND and OR from Logical AND and OR operators. If you use AND (&) operator, it generally means you are using it in the context of bitwise operations.

Example with Precedence or Priority Explained

In the below code example, Relational operator (>) takes higher priority. Short Circuit AND (&&) has got the least priority.

class OperatorPrecedence
{
  public static void main(String args[])
  {
    int a=5;
    int b=9;
    boolean c = a > 4 && true & b !=9;
    // Priority order: >, !=, &, &&
    // (a>4) && true & b!=9
    // true && true & b==9
    // true && true & false
    // true && false
    //false
    System.out.println(c);
  }
}
//OUTPUT: false

 

1. Logical Unary NOT (!) Operator

Logical Unary NOT operator requires just One Operand. It simply turns true to false and false to true. Its symbol is an Exclamation.

Truth Table of Logical Unary NOT
Expression Result
false true
true false

Example Usage:

 boolean show = true;
 show = !show;
 if(!show)
 {
   System.out.println("SHOW = false");
 }

2. Logical AND (&) Operator

Logical AND operator gives an output of true only if both operands are true. Logical AND operator checks the value of both operands or expressions before giving output. Even if the first expression is false, it goes for evaluating the second expression. This is a time waste thing and a drawback. Its symbol is an Ampersand.

Truth Table of Logical AND &
expression1 expression2 Result
false false false
false true false
true false false
true true true

Example Usage:

 int k=5, p=9;
 c = (k<4)&(p>5);
 //p>5 is evaluated. Time waste.
 if(c)
 {
   System.out.println("Logical AND");
 }

3. Logical Short Circuit AND (&&) Operator

Logical Short Circuit AND gives an output of true only if both Operands or Expressions are true. If the first expression is false, Short Circuit AND (&&) avoids evaluating the second expression. So it is faster than normal Logical AND (&) operator. Its symbol is Two Ampersands (&&).

Truth Table of Logical Short Circuit AND &&
expression1 expression2 Result
false false false
false true false
true false false
true true true

Example Usage:

 int k=5, p=9;
 c = (k<4)&&(p>5);
 //p>5 is not evaluated.
 if(!c)
 {
   System.out.println("Short Circuit Logical AND");
 }

4. Logical OR (|) Operator

The logical OR (|) operator gives an output of true if one of the operands is true. So a combination of true and false always gives true as the output. Logical OR evaluates the second expression or operand even if the first expression is true. So it is slow compared to Short Circuit Logical Operator (||). Its symbol is a PIPE.

Truth Table of Logical OR
expression1 expression2 Result
false false false
false true true
true false true
true true true

Example Usage:

 int k=5, p=9;
 c = (k>3)|(p>5);
 //p>5 is evaluated. Time waste.
 if(c)
 {
   System.out.println("Logical OR");
 }

5. Logical Short Circuit OR (||) Operator

The Logical Short Circuit OR (||) operator gives an output of true if one of the expressions or operands is true. It gives an output of true if the first expression is true without evaluating the second expression. So it is fast. Only if the first expression is false, the second expression is evaluated or executed by Short Circuit OR operator.

Truth Table of Logical Short Circuit OR
expression1 expression2 Result
false false false
false true true
true false true
true true true

Its symbol is Two Pipes (||).

Example Usage:

 int k=5, p=9;
 c = (k>3)||(p>5);
 //p>5 is not evaluated.
 if(c)
 {
   System.out.println("Short Circuit Logical OR");
 }

6. Logical Exclusive OR (^) Operator

The Logical Exclusive OR (^) operator gives an output of true if both operands are different. It gives an output of false if both the operands or expressions are the same. Its symbol is a CARAT.

Truth Table of Logical XOR / Exclusive OR
expression1 expression2 Result
false false false
false true true
true false true
true true false

Example Usage:

 int k=5, p=9;
 c = (k>3)^(p>9);
 if(c)
 {
   System.out.println("Logical XOR");
 }

 

Java Compound Logical Assignment Operators

There are only three Compound Logical Assignment operators in Java, AND, OR and Exclusive OR. Simply put an Equal To (=) symbol after the Logical AND, OR or XOR operators to turn it into a Compound Assignment operator.

Note: The compound assignment is not possible with Short Circuit AND (&&), Short Circuit OR (||) and Unary NOT(!) operators.

1. Compound Assignment AND (&=) Operator

Here "expression" should be boolean variable or constant. "var" is a variable.

Syntax:

var &= expression
var = var & expression
eg.
a &= false
a = a & false

2. Compound Assignment OR(|=) Operator

Here "expression" should be boolean variable or constant. "var" is a variable.

Syntax:

var |= expression
var = var | expression
eg.
a |= true
a = a | true

3. Compound Assignment Exclusive OR (^=) Operator

Here "expression" should be boolean variable or constant. "var" is a variable.

Syntax:

var ^= expression
var = var ^ expression
eg.
a ^= true
a = a ^ true

Example: Logical Compound Assignment Operators

class CompoundAssignmentOperators
{
  public static void main(String args[])
  {
    boolean a = true;
    boolean b= false;
    boolean c = true;
    boolean d = false;
    a &= false; //a = a & false = false
    b |= true; //b = b | true = true
    c ^= false; //c = c^false = true
    d &&= false; //Error. Not an Operator
    d ||= false; //Error
  }
}

In the next chapters, we shall discuss Bitwise Operators in Java with examples.