Unit 4: Iteration

AP Computer Science A

What you'll master in this unit

The three types of loops

Key loop patterns

Counting loop

java
for (int i = 0; i < 10; i++) {
    System.out.println(i);   // prints 0 through 9
}

Accumulator loop

java
int sum = 0;
for (int i = 1; i <= 100; i++) {
    sum += i;   // sum = 5050
}

Sentinel loop

java
while (input != -1) {
    // process input
    input = scanner.nextInt();
}

String traversal

java
String word = "Hello";
for (int i = 0; i < word.length(); i++) {
    String ch = word.substring(i, i + 1);
    System.out.println(ch);
}

Why Unit 4 matters