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80 lines
1.3 KiB
80 lines
1.3 KiB
package net.jrtechs.www.DataStructures.Lists.Stack;
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import net.jrtechs.www.DataStructures.Node;
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/**
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* @author Jeffery Russell 8-25-18
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* @param <E> generic stored in collection
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*/
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public class Stack<E> implements IStack<E>
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{
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/** Head node */
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private Node<E> head;
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public Stack()
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{
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this.head = null;
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}
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public Stack(E o)
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{
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this.head = new Node(o);
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}
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/**
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* Determines if the stack is empty
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*
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* @return
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*/
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@Override
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public boolean empty()
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{
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return (this.head == null);
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}
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/**
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* Retrieves top element with out removing it
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*
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* @return top element
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*/
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@Override
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public E peek()
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{
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if(this.head == null)
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return null;
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return head.getData();
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}
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/**
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* Returns and removes top element from
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* the stack.
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*
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* @return top element
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*/
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@Override
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public E pop()
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{
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if(this.empty())
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{
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return null;
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}
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E temp = this.head.getData();
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this.head = this.head.getNext();
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return temp;
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}
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/**
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* Adds a new element to the Stack.
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*
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* @param item to add to stack
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*/
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@Override
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public void push(E item)
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{
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this.head = new Node<>(item, this.head);
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}
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}
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