Java中参数以by value方式而非by reference 方式传递(值传递)

Java中参数以by value方式而非by reference 方式传递(值传递)
       很多人都普遍的认为：java中的参数以by reference方式传递。其实这是一个误解，参数其实是以by value 方式传递。这个误解源于【Java object 都是 object reference 】这一事实。下面我们来看一个实例：
[java] view plaincopyprint?
<PRE class=java name="code"><SPAN style="FONT-SIZE: 14px">      import java.awt.Point;

    public class PassByValue {

    public static void modifyPoint(Point pt,int j){
        pt.setLocation(5, 5);
        j=15;
        System.out.println("During modifyPoint " + "pt = " + pt + " and j = " + j);
    }

    public static void main(String args[]){
        Point p = new Point(0, 0);
        int i = 10;
        System.out.println("Before modifyPoint " + "p = " + p + " and i = " + i);
        modifyPoint(p, i);
        System.out.println("Before modifyPoint " + "p = " + p + " and i = " + i);
        }
    }</SPAN></PRE>
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SPAN style="FONT-SIZE: 14px">      import java.awt.Point;        public class PassByValue {        public static void modifyPoint(Point pt,int j){          pt.setLocation(5, 5);          j=15;          System.out.println("During modifyPoint " + "pt = " + pt + " and j = " + j);      }        public static void main(String args[]){          Point p = new Point(0, 0);          int i = 10;          System.out.println("Before modifyPoint " + "p = " + p + " and i = " + i);          modifyPoint(p, i);          System.out.println("Before modifyPoint " + "p = " + p + " and i = " + i);          }      }</SPAN>        import java.awt.Point;

 public class PassByValue {

 public static void modifyPoint(Point pt,int j){
  pt.setLocation(5, 5);
  j=15;
  System.out.println("During modifyPoint " + "pt = " + pt + " and j = " + j);
 }

 public static void main(String args[]){
  Point p = new Point(0, 0);
  int i = 10;
  System.out.println("Before modifyPoint " + "p = " + p + " and i = " + i);
  modifyPoint(p, i);
  System.out.println("Before modifyPoint " + "p = " + p + " and i = " + i);
  }

程序输出结果如下：

Before modifyPoint p = java.awt.Point[x=0,y=0] and i = 10
During modifyPoint pt = java.awt.Point[x=5,y=5] and j = 15
Before modifyPoint p = java.awt.Point[x=5,y=5] and i = 10

在此结果中整型的i值没有发生改变而Object类型的p的值却发生了变化，原因如下：
java 是通过值传递当（by value传递）当调用modifyPoint()方法并传值的时候，
整型值i会被copy一个复件传到方法中，而p是Point 的对象，
所以出入的时候是将P的引用值（reference）的复件传递过去，而不是将Point 的复件传递过去。
当运行完，modifyPoint()方法中对i的值修改只是对它的副本进行修改，所以对main中的i值没有影响，
而modifyPoint()方法中对Point 的对象的引用值（reference）的副本的修改将改变main中的Point的引用值，
所以将影响main中p的值。

补充：软件开发 , Java ,