LEARN JAVA : CONDITIONAL OPERATORS

CONDITIONAL OPERATORS

Introduction to Conditional Operators

Java includes operators that only use boolean values. These conditional operators help simplify complex boolean relationships by reducing multiple boolean values to a single value.

For example, what if we want to run a code block only if multiple conditions are true. We could use the AND operator: &&.

Or, we want to run a code block if at least one of two conditions are true. We could use the OR operator: ||.

Finally, we can produce the opposite value, where true becomes false and false becomes true, with the NOT operator: !.

We’ll explore each of these operators in this lesson to see how they clean up our conditional statements.

Conditional-And: &&

Let’s return to our student enrollment program. We’ve added an additional requirement: not only must students have the prerequisite, but their tuition must be paid up as well. We have two conditions that must be true before we enroll the student.

Here’s one way we could write the code:

if (tuitionPaid) {
  if (hasPrerequisite) {
    // enroll student
  }
}

We’ve nested two if-then statements. This does the job but we can be more concise with the AND operator:

if (tuitionPaid && hasPrerequisite) {
  // enroll student
}

The AND operator, &&, is used between two boolean values and evaluates to a single boolean value. If the values on both sides are true, then the resulting value is true, otherwise the resulting value is false.

This code illustrates every combination:

true && true
// true
false && true
// false
true && false
// false
false && false
// false


Conditional-Or: ||


The requirements of our enrollment program have changed again. Certain courses have prerequisites that are satisfied by multiple courses. As long as students have taken at least one prerequisite, they should be allowed to enroll.

Here’s one way we could write the code:

if (hasAlgebraPrerequisite) {
  // Enroll in course
}

if (hasGeometryPrerequisite) {
  // Enroll in course
}


We’re using two different if-then statements with the same code block. We can be more concise with the OR operator:

if (hasAlgebraPrerequisite || hasGeometryPrerequisite) {
  // Enroll in course
}


The OR operator, ||, is used between two boolean values and evaluates to a single boolean value. If either of the two values is true, then the resulting value is true, otherwise the resulting value is false.

This code illustrates every combination:

true || true
// true
false || true
// true
true || false
// true
false || false
// false

 

Logical NOT: !


The unary operator NOT, !, works on a single value. This operator evaluates to the opposite boolean to which it’s applied:

!false
// true
!true
// false


NOT is useful for expressing our intent clearly in programs. For example, sometimes we need the opposite behavior of an if-then: run a code block only if the condition is false.

boolean hasPrerequisite = false;

if (hasPrerequisite) {
  // do nothing
} else {
  System.out.println("Must complete prerequisite course!");
}


This code does what we want but it’s strange to have a code block that does nothing!

The logical NOT operator cleans up our example:

boolean hasPrerequisite = false;

if (!hasPrerequisite) {
  System.out.println("Must complete prerequisite course!");

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}


We can write a succinct conditional statement without an empty code block.



Summary :


Conditional operators work on boolean values to simplify our code. They’re often combined with conditional statements to consolidate the branching logic.

Conditional-AND, &&, evaluates to true if the booleans on both sides are true.

if (true && false) {
  System.out.println("You won't see me print!");
} else if (true && true) {
  System.out.println("You will see me #I'm Tushar :) ");
}


Conditional-OR, ||, evaluates to true if one or both of the booleans on either side is true.

if (false || false) {
  System.out.println("You won't see me print!");
} else if (false || true) {
  System.out.println("You will see me #I'm Tushar!");
}


Logical-NOT, !, evaluates to the opposite boolean value to which it is applied.

if (!false) {
  System.out.println("You will see this print, Follow me on Instagram : @tushargahora");
}