//封装一个类型的栈
public class aaa2
{

private int maxsize;
private double element[];
private int top;
public aaa2(int n)
{
maxsize=n;
top=0;
element =new double[n];
}

public double gettop()
{
if(isempty())
{ System.out.println("there is no element.");
return 0.0;
}
else

{ return element[top--];//注意return 一定放在最后

}
}
public void push(double a)
{
if(isfull())
System.out.println("there is full of element");
else
{ top++;
element[top]=a;
}
}
public boolean isfull()
{
return (top==maxsize);

}

public boolean isempty()
{
return (top==0);

}

}


public class aaaa2
{
public static void main(String args[])
{
aaa2 stack=new aaa2(3);
double a,b,c,d,m;
a=1.0;
b=20.2;
c=21.3;
d=25.6;
stack.push(a);
stack.push(b);
stack.push(c);

m=stack.gettop();
System.out.println("m="+m);
}
}


以上是我写地小程序，就是一个栈，然后进栈出栈，可是再编译时没问题，但运行时发现了越界地错误。ArrayIndexOutOfBoundsException,当我去掉 c=21.3; d=25.6;就没有这样的错误了。可是我明明在发生越界时会打印出

("there is full of element");，

怎么会发生这样地情况呢？谢谢大家。请看一下。由于条件有限，没法每天上网看，所以可能无法及时回复大家。

谢谢大家，我知道了，运行下来时对地，我觉得还有一种改法，//封装一个类型的栈
public class aaa2
{

private int maxsize;
private double element[];
private int top;
public aaa2(int n)
{
maxsize=n;
top=0;
element =new double[n];//改为 element =new double[n+1];
}

public double gettop()
{
if(isempty())
{ System.out.println("there is no element.");
return 0.0;
}
else

{ return element[top--];//注意return 一定放在最后

}
}
public void push(double a)
{
if(isfull())
System.out.println("there is full of element");
else
{ top++;
element[top]=a;
}
}
public boolean isfull()
{
return (top==maxsize);

}

这样运行下来也对地，谢谢啊