Three implementations of Java-Stack (array, container, linked list)

Source: https://segmentfault.com/a/1190000002516799

A stack is a linear list that restricts insertion and deletion operations to only one end of the list.
Java does not have a data structure like a stack. If you want to use a data structure like first-in-last-out (FILO), you must implement it yourself.

To implement Stack, it should at least include:
1. pop() pop operation, pop the top element of the stack.
2. push(E e) push operation
3. peek() to view the top element of the stack
4. isEmpty() stack is empty

In addition, when implementing a stack, several issues should be considered:
1. The initial size of the stack and how to add new stack space after the stack is full
2. Synchronization is required when updating the stack

There are three ways to implement it, array, container, and linked list.

data:

package     gsm;     import   java.util.*;   public class StackArray{ private int[] array;//implemented with array private int  top;  //Stack top pointer private final static int  size =  100; public StackArray(){ array =  new int[size]; top = -1; //When the stack is empty   } //Push onto the stack public void push(int  element){ if(top == size-1){        throw new  StackOverflowError(); }  else array[++top] = element; } //pop the stack public int pop(){ if( top == -1){        throw new     EmptyStackException(); }     return  array[top--]; }  //Judge whether it is empty public boolean isEmpty(){ return  top == -1; }    //Return the top element of the stack public  Integer  peek(){ if( top == -1){        throw new     EmptyStackException(); }     return  array[top]; } }  

container

package     gsm;     public interface Stack<T> { public T pop(); public void push(T  element); public boolean isEmpty(); public T peek(); }    package     gsm;     import   java.util.*;   public class StackList<T> implements Stack<T> { private List list ; //implemented with container  StackList(){ list =  new ArrayList(); }  //pop the stack public T pop(){ if(this.isEmpty() ==     true){        throw new     EmptyStackException(); }     return  list.remove(list.size()-1); }  //Push onto the stack public void push(T  element){ list.add(element); }  //Judge whether it is empty public boolean isEmpty(){ return  list.size() ==  0; }    //Return the top element of the stack public T peek(){ if(this.isEmpty() ==     true){        throw new     EmptyStackException(); }     return  list.get(list.size()-1); } }  

linked list

package     gsm;     import java.util.EmptyStackException; public class LinkedStack<T> implements Stack<T>{ //No need to store nodes in data structures such as containers or arrays //Node定义一个节点类 private static class Node<U>{ private  U item;  //Stored data private Node next; //Similar to pointer  Node(){  this.item =  null; this.next =  null; }    Node(U item, Node next){ this.item = item;  this.next = next; }  boolean end(){ return  item==  null  && next ==  null; } }  private Node top ; //Stack top pointer  LinkedStack(){ top =  new Node(); }  //pop the stack public T pop(){ if(this.isEmpty() ==     true){        throw new     EmptyStackException(); }     T result = top.item; if(!top.end()) { top =  top.next; } return  result; }  //Push onto the stack public void push(T  element){ top =  new Node(element, top); }    //Judge whether it is empty public boolean isEmpty(){ return  top.end(); }  //Return the top element of the stack public T peek(){ if(this.isEmpty() ==     true){        throw new     EmptyStackException(); }     T result = top.item; return  result; } }