例4-7和例4-8

class Tom{
 void f(int x,double y){
    x=x+1;
    y=y+1;
 System.out.printf("参数x和y的值分别是:%d,%3.2f\n",x,y);
}
}

public class Example4_7{
  public static void main(String args[]){
   int x=10;
   double y=12.58;
   Tom cat=new Tom();
   cat.f(x,y);
   System.out.printf("main方法中x和y的值仍然分别是:%d,%3.2f\n",x,y);
 }
}

class Jerry{
 int leg;
 Jerry(int n){
  leg=n;
 }
 void setLeg(int n){
  leg=n;
 }
 int getLeg(){
  return leg;
 }
}
class Tom{
 void f(Jerry mouse){
   mouse.setLeg(12);
   System.out.println("在执行方法f时,参数mouse修改了自己leg的值");
   System.out.println("当前参数mouse的成员leg的值:"+mouse.getLeg());
   mouse=null;
   //mouse.setLeg(12);
  }
 }

 public class Example4_8{
  public static void main(String args[]){
   Tom cat=new Tom();
   Jerry jerry=new Jerry(2);
   System.out.println("在调用方法f之前,jerry的成员leg的值:"+jerry.getLeg());
   cat.f(jerry);
   System.out.println("在调用方法f之后,jerry的成员leg的值:"+jerry.getLeg());
  }
 }