자바 연결리스트로 구현한 스택 (Java Linked List Queue)

오라클자바커뮤니티에서 설립한 오엔제이프로그래밍 실무교육센터

(신입사원채용무료교육, 오라클SQL, 튜닝, 힌트,자바프레임워크, 안드로이드, 아이폰, 닷넷)  

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public class EmptyStackException extends RuntimeException {
  public EmptyStackException()  {
      super ("The stack is empty.");
  }

  public EmptyStackException (String message)  {
      super (message);
  }
}



class ChainNode  {           
          Object element;
          ChainNode next;           
          ChainNode() {}     
          ChainNode(Object element) { this.element = element;}
          ChainNode(Object element, ChainNode next)  {
this.element = element;  this.next = next;
  }
}

public class LinkedStack implements Stack {
    protected ChainNode topNode;

    /** create an empty stack */   
    public LinkedStack() {       
topNode = new ChainNode();
 }

/** return true if stack is empty */
public boolean isEmpty() { 
return topNode.next == null; 
}

/** return top element of stack 
  * throws EmptyStackException when the stack is empty */
public Object peek() {
      if (isEmpty())      throw new EmptyStackException();
      return topNode.next.element;
}

/** add theElement to the top of the stack */
 public void push(Object theElement) { 
ChainNode p = new ChainNode(theElement, null); 
p.next = topNode.next;
topNode.next = p;
 }

 /** remove top element of stack and return it
    * throws EmptyStackException when the stack is empty */
 public Object pop() {
  if (isEmpty())    throw new EmptyStackException();
  Object topElement = topNode.next.element;
  topNode.next = topNode.next.next;
  return topElement;
 }

 public String  toString() {
 StringBuffer sb = new StringBuffer("[");
 ChainNode p = topNode.next;
 do  {
 if (p.element == null) sb.append("null");
 else sb.append(p.element.toString());
 p = p.next;
 if (p != null) sb.append(",");
 } while (p != null);
 sb.append("]");
 return sb.toString();
 }
}



public class Main {
  public static void main(String args[]) {   
      LinkedStack myStack = new LinkedStack();
      myStack.push("a");
      myStack.push("b");
      myStack.push("c");
  System.out.println(myStack);
  myStack.pop();   
    System.out.println(myStack);   
  System.out.print("현재 top pointer의 data : ");
    System.out.println(myStack.peek());
  }
}



interface Stack {   
            public boolean isEmpty();
            public Object peek();
            public void push(Object theObject);
            public Object pop();
}  

[출처] 오라클자바커뮤니티 - http://www.oraclejavanew.kr/bbs/board.php?bo_table=LecJavaAlgorithm&wr_id=52