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。