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Java If Else
Basic If Statement:
The if statement is a fundamental control structure that allows you to execute a block of code only if a specified condition is true. It is often used to make decisions in your code.
int number = 10;
if (number > 5) {
System.out.println("Number is greater than 5");
}
Console Output:
Number is greater than 5
If-Else Statement
If-Else Structure:
The if-else statement allows you to choose between two blocks of code. If the condition is true, the first block executes; otherwise, the second block runs.
int number = 3;
if (number > 5) {
System.out.println("Number is greater than 5");
} else {
System.out.println("Number is 5 or less");
}
Console Output:
Number is 5 or less
If-Else If-Else Chain
Multiple Conditions:
The if-else if-else chain allows you to test multiple conditions. The code block for the first true condition will execute.
int number = 10;
if (number < 5) {
System.out.println("Number is less than 5");
} else if (number == 5) {
System.out.println("Number is 5");
} else {
System.out.println("Number is greater than 5");
}
Console Output:
Number is greater than 5
Nested If Statements
Nested Conditions:
You can nest if statements to check multiple conditions. This is useful for more complex decision-making processes.
int number = 8;
if (number > 5) {
if (number < 10) {
System.out.println("Number is between 6 and 9");
}
}
Console Output:
Number is between 6 and 9
Using Logical Operators
Combining Conditions:
Logical operators such as && (AND) and || (OR) allow you to combine multiple conditions in a single if statement.
int age = 25;
if (age > 18 && age < 30) {
System.out.println("Age is between 19 and 29");
}
Console Output:
Age is between 19 and 29
If with Ternary Operator
Ternary Operator:
The ternary operator is a shorthand form of the if-else statement. It is useful for simple conditions and assignments.
int number = 7;
String result = (number % 2 == 0) ? "Even" : "Odd";
System.out.println(result);
Console Output:
Odd
If with Strings
String Comparison:
When comparing strings in Java, use the .equals() method instead of == to ensure correct comparison.
String name = "Alice";
if (name.equals("Alice")) {
System.out.println("Hello, Alice!");
}
Console Output:
Hello, Alice!
Handling Null with If
Null Check:
Always check for null before calling methods on objects to prevent NullPointerException.
String text = null;
if (text != null && text.equals("Hello")) {
System.out.println("Text is Hello");
} else {
System.out.println("Text is not Hello or is null");
}
Console Output:
Text is not Hello or is null
Switch vs. If-Else
When to Use:
While if-else is versatile, switch statements can be more efficient for multiple exact matches. However, switch does not handle ranges or complex conditions.
int day = 3;
switch (day) {
case 1:
System.out.println("Monday");
break;
case 2:
System.out.println("Tuesday");
break;
case 3:
System.out.println("Wednesday");
break;
default:
System.out.println("Other day");
}
Console Output:
Wednesday
If with Boolean Expressions
Boolean Logic:
Boolean expressions are often used directly in if statements to simplify code logic.
boolean isActive = true;
if (isActive) {
System.out.println("The system is active");
}
Console Output:
The system is active
