深入理解java参数传递 - 黑马程序员技术交流社区

package test;
/**
* @description Java中没有引用传递只有值传递
*/
class Person {
private String name;
private String sex;
public Person(String x, String y) {
this.name = x;
this.sex = y;
}
// 重写toString()方法，方便输出
public String toString() {
return name + " " + sex;
}
// 交换对象引用
public static void swapObject(Person p1, Person p2) {
Person tmp = p1;
p1 = p2;
p2 = tmp;
}
// 交换基本类型
public static void swapInt(int a, int b) {
int tmp = a;
a = b;
b = tmp;
}
// 交换对象数组
public static void swapObjectArray(Person[] p1, Person[] p2) {
Person[] tmp = p1;
p1 = p2;
p2 = tmp;
}
// 交换基本类型数组
public static void swapIntArray(int[] x, int[] y) {
int[] tmp = x;
x = y;
y = tmp;
}
// 改变对象数组中的内容
public static void changeObjectArray(Person[] p1, Person[] p2) {
Person tmp = p1[1];
p1[1] = p2[1];
p2[1] = tmp;
// 再将p1[1]修改
Person p = new Person("wjl", "male");
p1[1] = p;
}
// 改变基本类型数组中的内容
public static void changeIntArray(int[] x, int[] y) {
int tmp = x[1];
x[1] = y[1];
y[1] = tmp;
x[1] = 5;
}
}
public class ByValueTest {
public static void main(String[] args) {
// 建立并构造两个对象
Person p1 = new Person("Alexia", "female");
Person p2 = new Person("Edward", "male");
System.out.println("对象交换前：p1 = " + p1.toString());
System.out.println("对象交换前：p2 = " + p2.toString());
// 交换p1对象和p2对象
Person.swapObject(p1, p2);
// 从交换结果中看出，实际对象并未交换
System.out.println("\n对象交换后：p1 = " + p1.toString());
System.out.println("对象交换后：p2 = " + p2.toString());
// 建立两个对象数组
Person[] arraya = new Person[2];
Person[] arrayb = new Person[2];
// 分别构造数组对象
arraya[0] = new Person("Alexia", "female");
arraya[1] = new Person("Edward", "male");
arrayb[0] = new Person("jmwang", "female");
arrayb[1] = new Person("hwu", "male");
System.out.println('\n' + "对象数组交换前：arraya[0] = "
+ arraya[0].toString() + ", arraya[1] = "
+ arraya[1].toString());
System.out.println("对象数组交换前：arrayb[0] = "
+ arrayb[0].toString() + ", arrayb[1] = "
+ arrayb[1].toString());
// 交换这两个对象数组
Person.swapObjectArray(arraya, arrayb);
System.out.println('\n' + "对象数组交换后：arraya[0] = "
+ arraya[0].toString() + ", arraya[1] = "
+ arraya[1].toString());
System.out.println("对象数组交换后：arrayb[0] = "
+ arrayb[0].toString() + ", arrayb[1] = "
+ arrayb[1].toString());
// 建立两个普通数组
int[] a = new int[2];
int[] b = new int[2];
// 给数组个元素赋值
for (int i = 0; i < a.length; i++) {
a[i] = i;
b[i] = i + 1;
}
System.out.println('\n' + "基本类型数组交换前：a[0] = " + a[0] + ", a[1] = " + a[1]);
System.out.println("基本类型数组交换前：b[0] = " + b[0] + ", b[1] = " + b[1]);
// 交换两个基本类型数组
Person.swapIntArray(a, b);
System.out.println('\n' + "基本类型数组交换后：a[0] = " + a[0] + ", a[1] = " + a[1]);
System.out.println("基本类型数组交换后：b[0] = " + b[0] + ", b[1] = " + b[1]);
// 改变对象数组的内容
Person.changeObjectArray(arraya, arrayb);
System.out.println('\n' + "对象数组内容交换并改变后：arraya[1] = " + arraya[1].toString());
System.out.println("对象数组内容交换并改变后：arrayb[1] = " + arrayb[1].toString());
// 改变基本类型数组的内容
Person.changeIntArray(a, b);
System.out.println('\n' + "基本类型数组内容交换并改变后：a[1] = " + a[1]);
System.out.println("基本类型数组内容交换并改变后：b[1] = " + b[1]);
}
}

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