不理解Echo e2 = e1在Java中

我理解以下Java输出。不理解Echo e2 = e1在Java中

public class EchoTestDrive { 
    public static void main(String[] args){ 
     Echo e1 = new Echo(); 
     Echo e2 = new Echo(); 
     int x = 0; 
     while (x<4){ 
      e1.hello(); 
      e1.count = e1.count + 1; 
      if (x==3){ 
       e2.count = e2.count +1; 
      } 
      if(x>0){ 
       e2.count = e2.count + e1.count; 
      } 
      x = x+1; 
      System.out.println("e1.count is " + e1.count); 
      System.out.println("e2.count is " + e2.count); 
     } 
     System.out.println(e2.count); 
    } 
} 

class Echo { 
    int count = 0; 
    void hello(){ 
     System.out.println ("helloooooooo.."); 
    } 
}

输出

helloooooooo.. 
e1.count is 1 
e2.count is 0 
helloooooooo.. 
e1.count is 2 
e2.count is 2 
helloooooooo.. 
e1.count is 3 
e2.count is 5 
helloooooooo.. 
e1.count is 4 
e2.count is 10 
10

但是当我改变回声E2 =新回声（） - 回波E2 = E1，我不明白为什么输出是如此。

public class EchoTestDrive { 
    public static void main(String[] args){ 
     Echo e1 = new Echo(); 
     Echo e2 = e1; 
     int x = 0; 
     while (x<4){ 
      e1.hello(); 
      e1.count = e1.count + 1; 
      if (x==3){ 
       e2.count = e2.count +1; 
      } 
      if(x>0){ 
       e2.count = e2.count + e1.count; 
      } 
      x = x+1; 
      System.out.println("e1.count is " + e1.count); 
      System.out.println("e2.count is " + e2.count); 
     } 
     System.out.println(e2.count); 
    } 
} 

class Echo { 
    int count = 0; 
    void hello(){ 
     System.out.println ("helloooooooo.."); 
    } 
}

输出

helloooooooo.. 
e1.count is 1 
e2.count is 1 
helloooooooo.. 
e1.count is 4 
e2.count is 4 
helloooooooo.. 
e1.count is 10 
e2.count is 10 
helloooooooo.. 
e1.count is 24 
e2.count is 24 
24

我，当x = 0时，e1.count是1和e2.count是0 当x = 1时，e1.count是e1.count是2和e2.count是2.等

我希望有人解释它。

在此先感谢。

来源

2010-06-22 shin

当你有Echo e2 = e1;你做到这一点，所以e1和e2都指向相同的内存位置。因此，无论何时添加到e2，它都会添加到该内存位置，因此e1具有相同的值，反之亦然。具体地说

当x = 0

e1.hello(); 
     e1.count = e1.count + 1; //adds 1 to the memory location 
     if (x==3){ // x is 0 so doesn't go in 
      e2.count = e2.count +1; 
     } 
     if(x>0){ // x is 0 so doesn't go in 
      e2.count = e2.count + e1.count; 
     } 
     x = x+1; 
     System.out.println("e1.count is " + e1.count); 
     System.out.println("e2.count is " + e2.count); 
    } 
    System.out.println(e2.count); 
}

因此，存储器位置等于1和二者e1和e2是1

当x = 1

e1.hello(); 
     e1.count = e1.count + 1; 
      //adds 1 to the memory location which was already 1 from last time and now equals 2 
     if (x==3){ // x is 1 so doesn't go in 
      e2.count = e2.count +1; 
     } 
     if(x>0){ // x is 1 so goes in as 1 is greater than 0 
      e2.count = e2.count + e1.count; // adds e2 and e1 = 2 + 2 from previous line above = 4 
     } 
     x = x+1; 
     System.out.println("e1.count is " + e1.count); 
     System.out.println("e2.count is " + e2.count); 
    } 
    System.out.println(e2.count); 
}

因此所述存储器位置等于4并且e1和e2都是4

来源

2010-06-22 14:27:15 Kyra