メソッドとパラメータの定義

メソッドとは

メソッドシグネチャ

定義と呼び出し

public class Main {
  // Add two integers and return the sum
  static int add(int a, int b) {
    return a + b;
  }

  public static void main(String[] args) {
    // Call the method with arguments 2 and 3
    int result = add(2, 3);
    System.out.println("add(2, 3) = " + result);
  }
}

パラメーターと引数

public class Main {
  // Greet the user by name (parameter)
  static void greet(String name) {
    System.out.println("Hello, " + name + "!");
  }

  public static void main(String[] args) {
    // "Alice" is an argument; it is copied into parameter `name`
    greet("Alice");
    greet("Bob");
  }
}

戻り値と void

public class Main {
  // Convert Celsius to Fahrenheit and return the result
  static double cToF(double c) {
    double f = c * 9.0 / 5.0 + 32.0;
    return f;
  }

  // Print a line (no value returned)
  static void line() {
    System.out.println("----------");
  }

  public static void main(String[] args) {
    double out = cToF(25.0);
    System.out.println("25C -> " + out + "F");
    line();
  }
}

パラメーターの順序

public class Main {
  // Compute the area of a rectangle
  static int area(int width, int height) {
    return width * height;
  }

  public static void main(String[] args) {
    // Argument order must match parameter order by position
    int a1 = area(3, 5); // width=3, height=5
    int a2 = area(5, 3); // width=5, height=3
    System.out.println("area(3,5) = " + a1);
    System.out.println("area(5,3) = " + a2);
  }
}

シグネチャの確認

復習と次のステップ