Java Conditional (Java If ... Else)

Conditions and if statements let you control the flow of your program - deciding which code runs, and which code is skipped.

Basically:

Purpose: Control the flow of a program by deciding which code runs based on a condition.
Real‑life analogy:
If it rains → take an umbrella; else → do nothing.
Key point: Conditions must evaluate to true or false.

Java Conditional Keywords

Keyword	Purpose
`if`	Executes a block if the condition is true.
`else`	Executes a block if the same condition is false.
`else if`	Tests a new condition if the previous `if` or `else if` was false.
`switch`	Tests one variable against multiple possible values (alternative to many `else if`).

Proper Syntax and Structure

Basic If:

if (condition) {

// code runs if condition is true

}

If… else:

switch if (condition) {

    // code if true

} else {

// code if false

}

If…else if…else

if (condition1) {

// code if condition1 is true

} else if (condition2) {

// code if condition2 is true

} else {

// code if none are true

}

Comparison Operators in Conditions

Operators	Meaning
<	Less Than
<=	Less Than or Equal to
>	Greater Than
>=	Greater Than or Equal to
==	Equal to
!=	No Equal to

Example Statements:

Basic if

if (20 > 18) { System.out.println( “20 is greater than 18” ) }

Using Variables

int x = 20;
int y = 18;
if (x > y) {
    System.out.println("x is greater than y");
}

If Else

int time = 20;
if (time < 18) {
    System.out.println("Good day.");
} else {
    System.out.println("Good evening.");
}

If Else if Else

int age = 15;
if (age < 13) {
    System.out.println("You are a child");
} else if (age < 20) {
    System.out.println("You are a teenager");
} else {
    System.out.println("You are an adult");
}

With Boolean Variables

boolean isLightOn = true;
if (isLightOn) {
    System.out.println("The light is on.");
}

Java Short Hand If...Else (Ternary Operator)

Structure:

variable = (condition) ? expressionTrue : expressionFalse;

Example:

int time = 20;
String result = (time < 18) ? "Good day." : "Good evening.";
System.out.println(result);

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🔍 Quick Summary

• if → runs code if condition is true.

• else → runs code if condition is false.

• else if → checks additional conditions.

• Ternary operator → short form for simple if…else.

• Always ensure conditions return a Boolean.

8⃣ Common Mistakes to Avoid

Using = instead of == in comparisons.
Forgetting curly braces {} for multi‑line blocks.
Writing If or IF instead of lowercase if.