java形参实参

摘自http://blog.youkuaiyun.com/zhaoyue007101/article/details/7870560

（一）基本数据类型：传值，方法不会改变实参的值。

如int，string

（二）对象类型参数：传引用，<"方法体内改变形参引用，不会改变实参的引用">，<"但有可能改变实参对象的属性值">

String[]数组

（1）方法体内改变形参引用，但不会改变实参引用 ，实参值不变。

（2）方法体内，通过引用改变了实际参数对象的内容，注意是“内容”，引用还是不变的。

package com.fortest.code;

public class ParameterTest {
	
	static void forChange(String a, String b){
		a = a+","+b;
		b = a ;
	}
	
	static void forChange(String[] a){
		String tmp = a[0];
		a[0] = a[1];
		a[1] = tmp;
	}
	
	static void forChange(Person p){
		p.age = p.age+10;
	}
	
	static void forChangePoint(Person p){
		p = new Person(50);
	}
	
	public static void main(String[] args){

		String a = "a";
		String b = "b";
		System.out.println("before change, a="+a+",b="+b);
		forChange(a, b);
		System.out.println("after change, a="+a+",b="+b+"\n");
		
		String[] c = {"m","n"};
		System.out.println("before change, c[0]="+c[0]+",c[1]="+c[1]);
		forChange(c);
		System.out.println("after change, c[0]="+c[0]+",c[1]="+c[1]+"\n");
		
		Person p = new Person(20);
		System.out.println("before change, p.age="+p.age);
		forChange(p);
		System.out.println("after change, p.age="+p.age);
		forChangePoint(p);
		System.out.println("after change point, p.age="+p.age);
	}
	
	static class Person{
		public int age;
		public Person(){
			
		}
		public Person(int age){
			this.age = age;
		}
	}
}

输出结果

before change, a=a,b=b
after change, a=a,b=b


before change, c[0]=m,c[1]=n
after change, c[0]=n,c[1]=m


before change, p.age=20
after change, p.age=30
after change point, p.age=30