Java参数传递，值传递

问题：Java 中参数的传递是以什么方式传递的？

回答:

1. Java中参数类型传递都是值传递
2. 基本数据类型的值传递采用先对值进行拷贝再传递
3. 对象类型的值传递传递的是对象的地址
4. String 虽然是对象类型，但是它的参数传递方式和基本数据类型相同

1. 基本数据类型先对值进行拷贝再传递

public class ParameterPassingTest {    public void function1(int a){        a = 10;    }    public void function2(Dog dog){        dog.setName("paul");    }    public void function3(String str){        str = "changed";    }}

调用 function1() 查看当为基本数据类型的引用赋值时的变化：

System.out.println("++++++++++++++++++++");System.out.println("a:" + a);passing.function1(1);System.out.println("a:" + a);System.out.println("++++++++++++++++++++");

++++++++++++++++++++a:11a:11++++++++++++++++++++

a 的值不变，说明对基本类型的引用赋值不改变原来的值

2. 对象类型传递对象的地址

public class Dog {    private String name;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}

调用 function2() 查看当为对象类型的引用赋值时的变化：

System.out.println("++++++++++++++++++++");Dog dog = new Dog();dog.setName("Mike");System.out.println("Dog:" + dog.getName());passing.function2(dog);System.out.println("Dog:" + dog.getName());System.out.println("++++++++++++++++++++");

++++++++++++++++++++Dog:MikeDog:paul++++++++++++++++++++

name 改变：说明引用拿到了对象的地址，并通过地址对其值直接进行修改

3. String 类型是特例

System.out.println("++++++++++++++++++++");String str = "abc";System.out.println("str:" + str);passing.function3(str);System.out.println("str:" + str);System.out.println("++++++++++++++++++++");

“`
++++++++++++++++++++
str:abc
str:abc
++++++++++++++++++++
““
String 虽然是对象类型，但是其值传递结果和基本数据类型一样。

4. 例题