求助：关于对象参数传递的问题

[dagoufujingzhang001]

我在写一个程序，测试过程中发现对象的值传递有错误，由于我对对象的理解不是很深刻，一直没有有效的改正错误，希望有高人能指点一二。现在我写了一个测试用的程序，一共由两个类组成Company和ReaderTest，其中main函数在ReaderTest中，源代码如下：

/********************Company类开始***********************************/
public class Company {

public String name;
public Company[] next=new Company[5];//
public Company[] previous=new Company[5];//im Feld gespeichert

public Company(){//constructor without parameter
name="";
for(int i=0;i<this.next.length;i++){
this.next[i]=null;
this.previous[i]=null;
}
}

public Company(String name){
this.name=name;
for(int i=0;i<this.next.length;i++){
this.next[i]=new Company();
this.previous[i]=new Company();

}
}

public Company(String name, Company next, Company previous){
this.name=name;
this.next[0]=next;
this.previous[0]=previous;
for(int i=1;i<this.next.length;i++){
this.next[i]=new Company();
this.previous[i]=new Company();

}
} //constructor with parameter

public Company[] getNext(){
return next;
}

public void setNext(Company[] c){
this.next=c;
}

public void addNext(Company c){
int add=0;
for(int i=0;i<5;i++){
if(this.next[i].getName().compareTo("")==1)
//if((this.next[i].getName()).compareTo(new String())!=1)
//if(this.next[i].equals(null))
add=i;
}
this.next[add]=c;
}

/*public void delNext(){
not necessary for now!
}*/
public Company[] getPrevious(){
return previous;
}

public void setPrevious(Company[] c){
this.previous=c;
}

public void addPrevious(Company c){
int add=0;
for(int i=0;i<5;i++){
if(this.previous[i]==null)
add=i;
}
this.previous[add]=c;
}

// public void delPrevious(){}

public String getName(){
return this.name;
}

public void setName(String s){
this.name=s;
}
//this method return the number of the hinder companies
public int howManyNext(){
int a = 0;
//String empty=" ";
for(int r=0;r<this.next.length;r++){
//if(this.next[r]!=null)
if(!this.next[r].getName().equals(" "))
a=r;}
return a;
}

public void setDuplicate(Company c){
this.setName(c.getName());
this.setNext(c.getNext());
this.setPrevious(c.getPrevious());
}
}
/******************************company类结束************************/

/**************************ReaderTest类开始*************************/
public class ReaderTest {

public Company c1;

/** Creates a new instance of ReaderTest */
public ReaderTest() {
c1=new Company("Company1");
}


public static void main(String[] args){

Company c2=new Company();
Company c3=new Company("Company2");
Company c4=new Company("COMPANY4");
rt.c1.addNext(c3);
//c2=rt.c1;
c2.setDuplicate(rt.c1);
c2.addNext(c4);
System.out.println("the rt.c1 has the name: "+rt.c1.getName());
System.out.println("the c2 has the name: "+c2.getName());
System.out.println("rt.c1 has next company "+rt.c1.howManyNext()+".And its name is"+rt.c1.next[0].getName());
System.out.println("c2 has next company "+c2.howManyNext()+".And its name is"+c2.next[0].getName());

}
}
/***********************************ReaderTest类结束****************************/

问题1:在ReaderTest的构造函数里我生成了一个Company c1,并且该Company有个string name属性为Company1,然后在后面我在c1的next数组中加入了另一个company c3;接下来我通过company类中的setDuplicate函数将c1的属性赋给了另一个company c2(这里c2的name是空字符串),并且在c2的next数组中我加入了第四个company c4 (c4的name属性值是COMPANY3).然后通过下面的System.out输出,然后可以看到c2的name属性被改为了Company1,这是我想得到的,但是在最后输出c1.next[0](这里应当是company2,也就是c3的name属性才对)时,却变成了"COMPANY3",也就是c4的属性值.请问,我该怎么改,才能在输出c1.next[0]时正确输出呢?

[Dan1980]

java代码请括在

中，就不会乱了。

你的代码问题比较多，我替你整理了一下，基于效率考虑我做了比较大的改动，你可以参考一下：

// Company.java
public class Company { 
	private static final int CAPACITY = 5;
	private String name;
	private Company[] next = new Company[CAPACITY];
	private Company[] previous = new Company[CAPACITY];

	public Company() { }  // keep a default constructor
	
	public Company(String comName) {
		name = comName;
	}

	public Company(String comName, Company firstNext, Company firstPrevious) {
		this(comName);
		next[0] = firstNext; 
		previous[0] = firstPrevious; 
	}
	
	public Company[] getNext() {
		return next;
	}
	
	public void setNext(Company[] c) {
		next = c;
	}

	public void addNext(Company c) {
		for (int i = 0; i < CAPACITY; i++)
			if (next[i] == null) {
				next[i] = c;
				return;
			}
	}

	public Company[] getPrevious() {
		return previous;
	}
	
	public void setPrevious(Company[] c) { 
		previous = c;
	} 

	public void addPrevious(Company c) {
		for (int i = 0; i < CAPACITY; i++)
			if (previous[i] == null) {
				previous[i] = c;
				return;
			}
	}

	public String getName() {
		return name;
	}
	
	public void setName(String s) {
		name = s;
	}

	public int howManyNext() {
		int result = 0;
		for (int i = 0; i < CAPACITY; i++)
			if (next[i] != null) result++;
		return result;
	}

	public void setDuplicate(Company c) {
		setName(c.getName());
		setNext(c.getNext());
		setPrevious(c.getPrevious());
	}
	
}

[dagoufujingzhang001]

重贴company类.上面比较凌乱

public class Company {

public String name;
public Company[] next=new Company[5];//
public Company[] previous=new Company[5];//im Feld gespeichert

public Company(){//constructor without parameter
name="";
for(int i=0;i<this.next.length;i++){
this.next[i]=null;
this.previous[i]=null;
}
}

public Company(String name){
this.name=name;
for(int i=0;i<this.next.length;i++){
this.next[i]=new Company();
this.previous[i]=new Company();

}
}

public Company(String name, Company next, Company previous){
this.name=name;
this.next[0]=next;
this.previous[0]=previous;
for(int i=1;i<this.next.length;i++){
this.next[i]=new Company();
this.previous[i]=new Company();

}
} //constructor with parameter

public Company[] getNext(){
return next;
}

public void setNext(Company[] c){
this.next=c;
}

public void addNext(Company c){
int add=0;
for(int i=0;i<5;i++){
if(this.next[i].getName().compareTo("")==1)
//if((this.next[i].getName()).compareTo(new String())!=1)
//if(this.next[i].equals(null))
add=i;
}
this.next[add]=c;
}


public Company[] getPrevious(){
return previous;
}

public void setPrevious(Company[] c){
this.previous=c;
}

public void addPrevious(Company c){
int add=0;
for(int i=0;i<5;i++){
if(this.previous[i]==null)
add=i;
}
this.previous[add]=c;
}



public String getName(){
return this.name;
}

public void setName(String s){
this.name=s;
}

//this method return the number of the hinder companies
public int howManyNext(){
int a = 0;
//String empty=" ";
for(int r=0;r<this.next.length;r++){
//if(this.next[r]!=null)
if(!this.next[r].getName().equals(" "))
a=r;}
return a;
}

public void setDuplicate(Company c){
this.setName(c.getName());
this.setNext(c.getNext());
this.setPrevious(c.getPrevious());
}


}

[dagoufujingzhang001]

怎么还是排版有问题?麻烦大家凑合着看一下吧.
另一个问题就是,我通过company中的howManyNext()方法来计算在每个company实例中的next数组中有多少company.(next的定义为
public Company[] next=new Company[5];).howManyNext方法如下:
public int howManyNext(){
int a = 0;
for(int r=0;r <this.next.length;r++){
//if(this.next[r]!=null)
if(!this.next[r].getName().equals(" "))
a=r;}
return a;
}

在ReaderTest的main方法中,我给c1和c2的next数组中都只添加了一个company,可是为什么根据我的howManyNext方法计算出来的值却总是4呢?无论我试用任何在howManyNext方法中的if判断,结果都是4,可是只应该返回1才对啊.请高手指点.谢谢.

[yuchui]

你程序是不是有问题？

[java]
public class ReaderTest {

public Company c1;

/** Creates a new instance of ReaderTest */
public ReaderTest() {
c1 = new Company("Company1");
}

public static void main(String[] args) {

Company c2 = new Company();
Company c3 = new Company("Company2");
Company c4 = new Company("COMPANY4");
rt.c1.addNext(c3);
//c2=rt.c1;
c2.setDuplicate(rt.c1);
c2.addNext(c4);
System.out.println("the rt.c1 has the name: " + rt.c1.getName());
System.out.println("the c2 has the name: " + c2.getName());
System.out.println("rt.c1 has next company " + rt.c1.howManyNext() + ".And its name is" + rt.c1.next[0].getName());
System.out.println("c2 has next company " + c2.howManyNext() + ".And its name is" + c2.next[0].getName());

}
}
[/java]

[yuchui]

rt.c1.addNext(c3);
你rt 哪来的，你都能运行的好好的，佩服你

[yuchui]

你也不把你理想的输出 给我们

[dagoufujingzhang001]

多谢楼上的指点，但是问题只解决了一半，next无法被正确计数的问题解决了，但是问题1仍然没有解决。我运行了程序后输出结果如下：
RT.c11 has next company 1.And ITS name isCompany2
the rt.c11 has the name: Company1
the c21 has the name: Company1
rt.c11 has next company 2.And its name isCompany2
c21 has next company 2.And its name isCompany2
当我在c21(一个company)的next数组中再加入一个company后，为什么c11的next数组中也变成了两个company对象呢？因为开始我只加入了一个company啊？

[yuchui]

,但是在最后输出c1.next[0](这里应当是company2,也就是c3的name属性才对)时,却变成了"COMPANY3",也就是c4的属性值.请问,我该怎么改,才能在输出c1.next[0]时正确输出呢?


程序相当的有问题


public void addNext(Company c) {
int add = 0;
for (int i = 0; i < 5; i++) {
if (this.next[i].getName().compareTo("") == 1)
{
add = i;
}
}
System.out.println("add:"+add);
this.next[add] = c;
}

执行 c2.addNext(c4);

这时候，就将原先的c3 替换成 c4


你这个this.next[add] 这个add 永远都是0,

[Dan1980]

to 4楼：这个问题出在setNext()方法上，可以改成：

public void setNext(Company[] c) {
	System.arraycopy(c, 0, next, 0, c.length < CAPACITY ? c.length : CAPACITY);
}

当然，setPrevious()也需作类似更改。

[dagoufujingzhang001]

回六楼及八楼：rt就是一个ReaderTest，复制代码的时候少复制了一句。那个错误我已经明白了，象Dan1980那样加了一句return就好了。