In Scala IF ELSE can be used in two ways, as statements and as expressions.

General form of an if-else statement:

When we use if as statements, we evaluate a Boolean expression and based on the result of the Boolean expression the code executes a statement. In this case the statement does not return anything by default.

if(BooleanExpression)
{
statement or block 1
}
else
 {
statement or block 2

}

General form of an if-else expressions:

When we use if as expression, we evaluate a Boolean expression and based on the result of the Boolean expression the code executes a statement. But in this case the if expression return the result of if expression.

val response  = if(BooleanExpression) "condition match" else "condition does not match"

Example:

object Demo {
  def main(args: Array[String]) {
    val x = 20;
    val y = 30;
    var res = "";

    if (x < 20 || y > 30) {
      res = "x == 20 && y == 30";
    } else {
      res = "x != 20";
    }

    println(res);
    
    val res2 = if (x != 20) "x == 20" else "x !=20";
    
    println(res2);
    
    println(if (x != 20) "x == 20" else "x !=20");

  }
}

/*
x != 20
x !=20
x !=20

*/

Logical Operators

• Scala provides logical operators.
  • The binary logical operators combine two boolean expressions into one.
  • The unary logical operator switches the value of a boolean expression.

• Binary logical operators have lower precedence than relational operators (they will be evaluated after)
• NOT has the same precedence as negation.

 

Operator	Meaning	Kind
&&	AND	Binary
||	OR	Binary
!	NOT	Unary

 

Logical Operator Practice

• 2 > 3 && 4 < 5
  • false – first operand is false
• 2 < 3 && 4 < 5
  • true
• 2 > 3 || 4 < 5
  • true
• 2 > 3 || 4 > 5
  • false – both operands are false
• !(2 > 3)
  • true – operand is false