我创建了一个基于DataRecord的堆栈数组。 这两个类都编译时没有错误,但是当我将push()写入堆栈时,它会改变stackArray []的每个索引中的数据。
我无法找到导致此问题的代码行。 请帮助我找到原因,谢谢。
DataRecord类:
public class DataRecord
{
private String id;
private String data;
//default constructior
public DataRecord( )
{
this.id = " ";
this.data = " ";
}
//overloded constructor
public DataRecord( String id, String data )
{
this.id = id;
this.data = data;
}
//set method
public void setIDandData( String id, String data )
{
this.id = id;
this.data = data;
}
//get method
public String getID()
{
return id;
}
public String getData()
{
return data;
}
//toString
public String toString()
{
return "\n Your ID is : " + id +
"\n Your DataRecord is : " + data + "\n";
}
}//End of DataRecord
MyStack1课程:
class MyStack1
{
private int maxSize;
private DataRecord[] stackArray;
private int top;
private String tempString = "";
public MyStack1(int sizeOfStack)
{
maxSize = sizeOfStack;
stackArray = new DataRecord[maxSize];
top = -1;
}
public void push( DataRecord userInput )
{
stackArray[++top] = userInput;
}
public DataRecord pop()
{
return stackArray[top--];
}
public String toString()
{
tempString = "";
for(int i = 0; i <= top; i++)
{
tempString += i+1 + stackArray[i].toString();
}
return "\nThe max size of the stack is : " + maxSize +
"\nThe top index of the stack is : " + top +
"\nThe top element of the stack is : " + stackArray[top] +
"\nThe list of element in the stack is : " +
"\n" + tempString;
}
public static void main(String[] args)
{
MyStack1 stackArray = new MyStack1( 5 );
DataRecord newData = new DataRecord(" Hello "," world! ");
stackArray.push(newData);
System.out.println("Results : " + stackArray.toString());
newData.setIDandData("why","omg");
stackArray.push( newData );
System.out.println("Results : " + stackArray.toString());
System.out.println("pop :"+stackArray.pop().toString());
System.out.println("pop :"+stackArray.pop().toString());
}
}
编译运行时,输出如上图所示。
答案 0 :(得分:2)
DataRecord newData = new DataRecord(" Hello "," world! ");
stackArray.push(newData);
System.out.println("Results : " + stackArray.toString());
newData.setIDandData("why","omg");
stackArray.push( newData );
第newData.setIDandData
行是修改已放入的对象。您必须明确创建新的DataRecord
; Java不会隐式复制对象。当您将newData
推入堆栈时,它会推送对该对象的引用;在一个地方修改该对象仍然会修改您放入堆栈的对象。
没有办法解决这个问题;这就是Java的工作原理。