class Demo<T>{
private T[] item;
private int i;
public Demo(int count){
item=new T[count];
i=0;
}
public void push(T item){
T[i++]=item;
}
public T Pop(){
return T[--i];
}
public static void main(String[] args){
Demo<int> de=new Demo<int>(7);
for(int i=0;i<7;i++){
de.push(i);
}
for(int i=0;i<7;i++){
System.out.print(de.Pop());
}
}
}
我以前搞c#这样可以在java中报错item=new T[count];好像构造函数不能这样写该怎么样实现？
private T[] item;
private int i;
public Demo(int count){
item=new T[count];
i=0;
}
public void push(T item){
T[i++]=item;
}
public T Pop(){
return T[--i];
}
public static void main(String[] args){
Demo<int> de=new Demo<int>(7);
for(int i=0;i<7;i++){
de.push(i);
}
for(int i=0;i<7;i++){
System.out.print(de.Pop());
}
}
}
我以前搞c#这样可以在java中报错item=new T[count];好像构造函数不能这样写该怎么样实现？
class Demo{
int count;
public Demo(int c){
this.count=c;
}
public static void main(String[] args){
Stack s=new Stack();
Demo d;
for(int i=0;i<7;i++){
d=new Demo(i);
s.push(d.count);
}
for(int i=0;i<7;i++){
System.out.println(s.pop());
}
}
}
package java.util;/**
* The <code>Stack</code> class represents a last-in-first-out
* (LIFO) stack of objects. It extends class <tt>Vector</tt> with five
* operations that allow a vector to be treated as a stack. The usual
* <tt>push</tt> and <tt>pop</tt> operations are provided, as well as a
* method to <tt>peek</tt> at the top item on the stack, a method to test
* for whether the stack is <tt>empty</tt>, and a method to <tt>search</tt>
* the stack for an item and discover how far it is from the top.
* <p>
* When a stack is first created, it contains no items.
*
* @author Jonathan Payne
* @version 1.28, 12/19/03
* @since JDK1.0
*/
public
class Stack<E> extends Vector<E> {
/**
* Creates an empty Stack.
*/
public Stack() {
} /**
* Pushes an item onto the top of this stack. This has exactly
* the same effect as:
* <blockquote><pre>
* addElement(item)</pre></blockquote>
*
* @param item the item to be pushed onto this stack.
* @return the <code>item</code> argument.
* @see java.util.Vector#addElement
*/
public E push(E item) {
addElement(item); return item;
} /**
* Removes the object at the top of this stack and returns that
* object as the value of this function.
*
* @return The object at the top of this stack (the last item
* of the <tt>Vector</tt> object).
* @exception EmptyStackException if this stack is empty.
*/
public synchronized E pop() {
E obj;
int len = size(); obj = peek();
removeElementAt(len - 1); return obj;
} /**
* Looks at the object at the top of this stack without removing it
* from the stack.
*
* @return the object at the top of this stack (the last item
* of the <tt>Vector</tt> object).
* @exception EmptyStackException if this stack is empty.
*/
public synchronized E peek() {
int len = size(); if (len == 0)
throw new EmptyStackException();
return elementAt(len - 1);
} /**
* Tests if this stack is empty.
*
* @return <code>true</code> if and only if this stack contains
* no items; <code>false</code> otherwise.
*/
public boolean empty() {
return size() == 0;
} /**
* Returns the 1-based position where an object is on this stack.
* If the object <tt>o</tt> occurs as an item in this stack, this
* method returns the distance from the top of the stack of the
* occurrence nearest the top of the stack; the topmost item on the
* stack is considered to be at distance <tt>1</tt>. The <tt>equals</tt>
* method is used to compare <tt>o</tt> to the
* items in this stack.
*
* @param o the desired object.
* @return the 1-based position from the top of the stack where
* the object is located; the return value <code>-1</code>
* indicates that the object is not on the stack.
*/
public synchronized int search(Object o) {
int i = lastIndexOf(o); if (i >= 0) {
return size() - i;
}
return -1;
} /** use serialVersionUID from JDK 1.0.2 for interoperability */
private static final long serialVersionUID = 1224463164541339165L;
}
//实现一个栈操作，将1~12月的英文单词压入栈中，然后在将其取出，使用Java代码实现 [SAP公司2005年10月面试题]
import java.util.*;public class Stacks
{
static String[] months = {"January", "February","March","April","May","June",
"July","August", "September", "October", "November", "December"};
public static void stackByStack()
{
Stack stk = new Stack();
for( int i = 0; i < months.length; i++ )
stk.push( months[i] + " ");
System.out.println( "stk = " + stk );
// stk.addElement( "The last line " );
// System.out.println( "element 2 =" + stk.elementAt( 2 ));
System.out.println( "出栈:" );
while( !stk.empty() )
System.out.println( stk.pop() );
}
public static void stackByVector()
{
Vector vq = new Vector();
for( int i = 0; i < months.length; i++ )
vq.addElement( months[i] + " " );
System.out.println( vq );
if ( vq.isEmpty() )
System.out.println("为空");
System.out.println("出栈：");
while( !vq.isEmpty() )
{
System.out.println( vq.lastElement() );//如果按先进先出，则改为vq.firstElement()
vq.removeElement( vq.lastElement() );
}
vq.clear();
}
public static void main(String[] arg)
{
stackByStack(); //使用Stack实现
stackByVector(); //使用Vector实现
}
}