Conditional statements and logical operators

Making decisions

Programs often need to do different things in different situations. A conditional statement runs a block of code only when a condition is true.

int marks = 72;

if (marks >= 40) {
    System.out.println("You passed.");
} else {
    System.out.println("Try again next time.");
}

The condition inside the parentheses must be a boolean expression. Exactly one of the two blocks runs.

Several possibilities with else if

int marks = 72;
String grade;

if (marks >= 90) {
    grade = "A";
} else if (marks >= 75) {
    grade = "B";
} else if (marks >= 60) {
    grade = "C";
} else {
    grade = "Needs improvement";
}

System.out.println(grade); // C

Java checks the conditions from top to bottom and runs the first block whose condition is true. Order matters: if you checked marks >= 60 first, a score of 95 would wrongly get a C.

Logical operators

int age = 22;
boolean hasId = true;

if (age >= 18 && hasId) {
    System.out.println("Entry allowed");
}

boolean isWeekend = false;
boolean isHoliday = true;
if (isWeekend || isHoliday) {
    System.out.println("Office closed");
}

if (!hasId) {
    System.out.println("Please bring an ID card");
}

Java uses short-circuit evaluation: in a && b, if a is false, b is never checked; in a || b, if a is true, b is skipped. This lets you write safe checks such as name != null && name.length() > 0.

The switch expression

When you compare one value against many fixed options, a switch is easier to read. Modern Java (14+) supports a concise arrow form that returns a value:

int day = 3;
String name = switch (day) {
    case 1 -> "Monday";
    case 2 -> "Tuesday";
    case 3 -> "Wednesday";
    case 4 -> "Thursday";
    case 5 -> "Friday";
    case 6, 7 -> "Weekend";
    default -> "Invalid day";
};
System.out.println(name); // Wednesday

The default branch handles every value not listed. Use switch for exact matches and if chains for ranges such as marks >= 75.

Walkthrough: a ticket price calculator

int age = 67;
boolean isStudent = false;
int price;

if (age < 5) {
    price = 0;
} else if (age >= 60 || isStudent) {
    price = 100;
} else {
    price = 200;
}
System.out.println("Ticket price: ₹" + price); // Ticket price: ₹100

Trace it: age < 5 is false, so Java checks the next condition. age >= 60 is true, so the OR expression is true without checking isStudent, and the price is 100.