Conditions and Loops

Programs become useful when they make decisions and repeat work. Java gives you clear, predictable tools for both.

if and else

Conditions must be boolean. Java will not treat a number as true or false.

int score = 72;

if (score >= 70) {
    System.out.println("A");
} else if (score >= 60) {
    System.out.println("B");
} else {
    System.out.println("Keep working");
}

switch

Modern Java switch expressions return a value and use arrow syntax. They are clearer than long if chains on one variable.

String level = "SS2";

String stage = switch (level) {
    case "SS1" -> "Junior";
    case "SS2", "SS3" -> "Senior";
    default -> "Unknown";
};

System.out.println(stage);

Loops

Use for when you know how many times to repeat. Use while when you repeat until a condition changes.

for (int i = 1; i <= 5; i++) {
    System.out.println("Week " + i);
}

int countdown = 3;
while (countdown > 0) {
    System.out.println(countdown);
    countdown--;
}

Practice

1. Print the grade for a score using if and else-if.
2. Use a switch to map a day number to a day name.
3. Print the numbers 1 to 20, but only the even ones.

Hands-on exercise

Write a program that prints the 7 times table from 1 to 12 in the form:
7 x 1 = 7
7 x 2 = 14
... using a for loop.

Recap

if chooses between branches, switch maps one value to one result, and loops repeat work.