The formal parameters of the method

package basic.java;

public class ParametersOfTheMethod {
    public static void main(String[] args) {
        int a = 10;
        int b = 20;

        System.out.println(a + "===" + b);

        change(a, b);

        System.out.println(a + "===" + b);
    }

    public static void change(int a, int b) {
        // TODO Auto-generated method stub
        System.out.println(a + "===" + b);
        a = b;
        b = a + b;
        System.out.println(a + "===" + b);
    }

}

如果方法的参数是基本数据类型：形式参数的改变不影响实际参数。

package basic.java;

public class ArgsDemo2 {
    public static void main(String[] args) {
        int arr[] = { 1, 2, 3, 4, 5 };

        for (int i = 0; i < arr.length; i++) {
            System.out.println(arr[i]);
        }

        change(arr);

        for (int i = 0; i < arr.length; i++) {
            System.out.println(arr[i]);
        }
    }

    public static void change(int[] arr) {
        // TODO Auto-generated method stub
        for (int i = 0; i < arr.length; i++) {
            if (0 == arr[i] % 2) {
                arr[i] *= 2;
            }
        }
    }
}

如果参数是引用数据类型：形式参数的改变直接影响实际参数。