自定义栈Stack 和 队列Queue

Posted 2022-03-27 tk55

自定义栈

 

接口

package com.test.custom;

public interface IStack<E> 
     E pop();
     void push(E e);
     E peek();
     int size();
     boolean empty();
     void clear();

实现类

package com.test.custom;

import java.util.ArrayList;
import java.util.EmptyStackException;
import java.util.List;

public class CustomStack<E> implements IStack<E>
    
    List<E> list =new ArrayList<E>();
    

    @Override
    public E pop() 
        // TODO Auto-generated method stub
        E e = peek();
        list.remove(list.size()-1);
        
        return e;
    

    @Override
    public void push(E e) 
        // TODO Auto-generated method stub
        list.add(e);
    

    @Override
    public E peek() 
        // TODO Auto-generated method stub
        int len = list.size();
        if(len==0)
            throw new EmptyStackException();
        
        return list.get(len-1);
    

    @Override
    public int size() 
        // TODO Auto-generated method stub
        return list.size();
    

    @Override
    public boolean empty() 
        // TODO Auto-generated method stub
        return size()==0;
    

    @Override
    public void clear() 
        // TODO Auto-generated method stub
        list.clear();
    

 

测试

package com.test.custom;

public class TestStack 
     public static void main(String[] args) 
         
        
        CustomStack<String> stack =new CustomStack<String>();
        for(int i =0 ; i < 4 ; i++)
            stack.push(""+(char)(‘A‘+i));
        


        System.out.println(stack.peek());
        System.out.println(stack.size());
        System.out.println(stack.pop());
        System.out.println(stack.size());
        System.out.println(stack.peek());
        stack.push("hello");
        System.out.println(stack.size());
        for(int i=0;i<5;i++)
        System.out.println(stack.pop());
        System.out.println(stack.size());
        

    

 

 

---

自定义队列

接口

package com.test.custom;

public interface IQueue<E> 
     boolean offer(E e); //超过容量就抛出 IllegalStateException
     E peek();//获取列头不移除，队列为null返回null
     E poll(); //获取并且移除列头
     int size();
     boolean isEmpty();

 

package com.test.custom;

import java.util.ArrayList;
import java.util.List;

public class CustomQueue<E> implements IQueue<E>
    
    List<E> list =new ArrayList<E>();
    private int size;
    @Override
    public boolean offer(E e) 
        // TODO Auto-generated method stub
        if(list.size()>=size)
            throw new IllegalArgumentException();
        
        list.add(e);
        return true;
    

    @Override
    public E peek() 
        // TODO Auto-generated method stub

        if(size() == 0) return null;
        return list.get(0);
    

    @Override
    public E poll() 
        // TODO Auto-generated method stub
        E e = peek();
        if(size()>0) list.remove(0);
        return e;
    

    @Override
    public int size() 
        // TODO Auto-generated method stub
        return list.size();
    

    @Override
    public boolean isEmpty() 
        // TODO Auto-generated method stub
        return list.size()==0;
    

    public CustomQueue(int size) 

        this.size = size;
    


    
     

测试

package com.test.custom;

public class TestQueue 
      public static void main(String[] args) 
          CustomQueue<String> stack =new CustomQueue<String>(4);
          for(int i =0 ; i < 4 ; i++)
              stack.offer(""+(char)(‘A‘+i));
          


          System.out.println(stack.peek());
          System.out.println(stack.size());
          
          System.out.println(stack.poll());
          System.out.println(stack.size());
          
          System.out.println(stack.peek());
          System.out.println(stack.size());
          
          stack.offer("hello");
          System.out.println(stack.size());
          
          for(int i=0;i<5;i++)
          System.out.println("i:"+stack.poll());

          
          
          for(int i =0 ; i < 5 ; i++)
              stack.offer(""+(char)(‘A‘+i));