Practice›Java Fundamentals›Module 3. Methods ›3.4 Scope and helpers

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3.4 Methods — calling a helper method

Lesson

A method can call another method

Methods don't only get called from main — one method can call another. A method that does a small job for another is a helper. Calling helpers lets you build a bigger result out of smaller, tested pieces.

Worked example

int square(int n) {
    return n * n;
}
int sumOfSquares(int a, int b) {
    return square(a) + square(b);   // calls the helper twice
}

System.out.println(sumOfSquares(3, 4));   // 9 + 16 = 25

▶ Try it: sumOfSquares calls the helper square. Run this, then change the two arguments and re-run.

public class Main {
    static int square(int n) {
        return n * n;
    }
    static int sumOfSquares(int a, int b) {
        return square(a) + square(b);
    }
    public static void main(String[] args) {
        System.out.println(sumOfSquares(3, 4));
    }
}

square(n) returns n * n. sumOfSquares(a, b) returns square(a) + square(b). What does sumOfSquares(3, 4) give?

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Can one method call another method?

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Assemble the body of sumOfSquares using the helper square.

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True or false?

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Type exactly what this program prints.

public class Main {
    static int half(int n) {
        return n / 2;
    }
    static int halfSum(int a, int b) {
        return half(a) + half(b);
    }
    public static void main(String[] args) {
        System.out.println(halfSum(10, 6));
    }
}

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