Processing: Logical Operators

Processing supports three logical operators, These are &&(AND), || (OR), and !(NOT)

Logical AND is also called Conditional AND

Logical OR is also called Conditional OR

Logical AND, OR are called Short circuit operators, will see why these are called short circuit soon.

Logical AND Operator

Operand1	Operand2	Evaluates To
true	true	true
true	false	false
false	true	false
false	false	false

Operators.pde

boolean operand1 = true;
boolean operand2 = true;
println((operand1 && operand2)); 

operand1 = true;
operand2 = false;
println((operand1 && operand2)); 

operand1 = false;
operand2 = true;
println((operand1 && operand2)); 

operand1 = false;
operand2 = false;
println((operand1 && operand2));

Output

true

false

false

false

Why Logical AND is called short circuit operator?

Since if the first statement in the expression evaluates to false, then Processing won't evaluate the entire expression. So, Logical AND is called short circuit AND

Operators.pde

int a = 10, b=21;

if( (a>b) && (a++ > b) ){
 println("This statement not evaluated");
}

println("a is not incremented " + a);

if( (a<b) && (a++ < b) ){
 println("This statement is evaluated");
} 

println("a is not incremented " + a);

Output

a is not incremented 10

This statement is evaluated

a is not incremented 11

Observation

In the expression (a>b) && (a++ > b), a>b is false, so && operator won't evaluate second statement in the expression, so a is not incremented.

Logical OR Operator

Operand1	Operand2	Evaluates To
true	true	true
true	false	false
false	true	false
false	false	false

As shown in the above table, || operator returns true if any of the operand evaluates to true, otherwise returns false.

Operators.pde

boolean operand1 = true;
boolean operand2 = true;
println((operand1 || operand2)); 

operand1 = true;
operand2 = false;
println((operand1 || operand2)); 

operand1 = false;
operand2 = true;
println((operand1 || operand2)); 

operand1 = false;
operand2 = false;
println((operand1 || operand2));

Output

true

true

true

false

Why Logical OR is called short circuit operator

Since if the first statement evaluates to true, then Processing won't evaluate the entire expression. So Logical OR is called short circuit OR

Operators.pde

int a = 10, b=21;

if( (a<b) || (a++ < b) ){
 println("This statement evaluated");
}
println("a is not incremented " + a);

if( (a>b) || (a++ > b) ){
 println("This statement is evaluated");
} 
println("a is incremented " + a);

Output

This statement evaluated

a is not incremented 10

a is incremented 11

Logical (!)NOT operator

Operand	Evaluates to
true	false
false	true

Operators.pde

boolean a = true;
println((!a));

a = false;
println((!a));

Output

false

true

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