Operators and Control Flow

if and else work as you'd expect from any C-family language — a condition in parentheses, followed by a block.

Main.java

public class Main {
    public static void main(String[] args) {
        int number = 7;
        if (number % 2 == 0) {
            System.out.println(number + " is even");
        } else {
            System.out.println(number + " is odd");
        }
    }
}

Output

7 is odd

for and while

A classic for loop declares an index, a condition, and an increment all in its header. while just repeats as long as its condition holds, with no built-in index at all.

Main.java

Try it yourself →

public class Main {
    public static void main(String[] args) {
        for (int i = 0; i < 3; i++) {
            System.out.println("i = " + i);
        }
        int count = 0;
        while (count < 3) {
            System.out.println("count = " + count);
            count++;
        }
    }
}

Output

i = 0
i = 1
i = 2
count = 0
count = 1
count = 2

switch

switch compares a value against a series of constant cases, falling through to the next case unless you break. default catches anything not matched above it.

Main.java

Try it yourself →

public class Main {
    public static void main(String[] args) {
        int day = 3;
        switch (day) {
            case 1:
                System.out.println("Monday");
                break;
            case 3:
                System.out.println("Wednesday");
                break;
            default:
                System.out.println("Unknown");
        }
    }
}

Output

Wednesday

Next: methods — defining methods, parameters, return types, and method overloading.

Practice exercise

Set a variable score of type int to 73. Print "pass" if score is 60 or above, otherwise print "fail".

← Variables and Types Methods →