栈（基于数组和链表）

栈是一个概念上的辅助工具，提供限定性的访问方法，使程序易读且不易出错。时间复杂度为O(1)。

基于数组的栈

package datastructure.c4.stack.stackdef;

public class StackX {
	private int maxSize;
	private long[] stackArray;
	private int top;
	public StackX(int s){
		maxSize=s;
		stackArray=new long[maxSize];
		top=-1;
	}
	public void push(long j){
		stackArray[++top]=j;
	}
	public long pop(){
		return stackArray[top--];
	}
	public long peek(){
		return stackArray[top];
	}
	public boolean isEmpty(){
		return (top==-1);
	}
	public boolean isFull(){
		return (top==maxSize-1);
	}
}

package datastructure.c4.stack.stackdef;

public class StackApp {
	public static void main(String[] args) {
		StackX theStack=new StackX(10);
		theStack.push(20);
		theStack.push(40);
		theStack.push(60);
		theStack.push(80);
		
		while(!theStack.isEmpty()){
			long value=theStack.pop();
			System.out.print(value);
			System.out.print("  ");
		}
		System.out.println("");
	}
}

案例1：字符反转

package datastructure.c4.stack.reverse;

public class StackX {
	private int maxSize;
	private char[] stackArray;
	private int top;
	public StackX(int max){
		maxSize=max;
		stackArray=new char[maxSize];
		top=-1;
	}
	public void push(char j){
		stackArray[++top]=j;
	}
	public char pop(){
		return stackArray[top--];
	}
	public char peek(){
		return stackArray[top];
	}
	public boolean isEmpty(){
		return (top==-1);
	}
	public boolean isFull(){
		return (top==maxSize-1);
	}
}

package datastructure.c4.stack.reverse;

public class Reverser {
	private String input;
	private String output;
	public Reverser(String in){
		input=in;
	}
	public String doRev(){
		int stackSize=input.length();
		StackX theStack=new StackX(stackSize);
		for(int j=0;j<input.length();j++){
			char ch=input.charAt(j);
			theStack.push(ch);
		}
		output="";
		while(!theStack.isEmpty()){
			char ch = theStack.pop();
			output+=ch;
		}
		return output;
	}
}

package datastructure.c4.stack.reverse;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class ReverseApp {
	public static void main(String[] args) throws IOException {
		String input,output;
		while(true){
			System.out.print("Enter a string:");
			System.out.flush();
			input=getString();
			if("".equals(input)){
				break;
			}
			Reverser theReverser=new Reverser(input);
			output = theReverser.doRev();
			System.out.println("Reversed:"+output);
		}
	}
	public static String getString() throws IOException{
		InputStreamReader isr = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(isr);
		String s = br.readLine();
		return s;
	}
}

案例2：括号对检查

package datastructure.c4.stack.brackets;

public class StackX {
	private int maxSize;
	private char[] stackArray;
	private int top;
	public StackX(int max){
		maxSize=max;
		stackArray=new char[maxSize];
		top=-1;
	}
	public void push(char j){
		stackArray[++top]=j;
	}
	public char pop(){
		return stackArray[top--];
	}
	public char peek(){
		return stackArray[top];
	}
	public boolean isEmpty(){
		return (top==-1);
	}
	public boolean isFull(){
		return (top==maxSize-1);
	}
}

package datastructure.c4.stack.brackets;

public class BracketChecker {
	private String input;
	public BracketChecker(String in){
		input=in;
	}
	public void check(){
		int stackSize=input.length();
		StackX theStack=new StackX(stackSize);
		
		for(int j=0;j<input.length();j++){
			char ch = input.charAt(j);
			switch (ch) {
			case '{':
			case '[':
			case '(':
				theStack.push(ch);
				break;
			case '}':
			case ']':
			case ')':
				if(!theStack.isEmpty()){
					char chx = theStack.pop();
					if(	(ch=='}' && chx!='{') ||
						(ch==']' && chx!='[') ||
						(ch==')' && chx!='(')){
						System.out.println("Error:"+ch+" at "+j);
					}
				}else{
					System.out.println("Error:"+ch+" at "+j);
				}
				break;
			default:
				break;
			}
		}
		if(!theStack.isEmpty()){
			System.out.println("Error:missing right delimiter");
		}else{
			System.out.println("Freedom from delimiter error");
		}
	}
}

package datastructure.c4.stack.brackets;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class BracketsApp {
	public static void main(String[] args) throws IOException {
		String input;
		while(true){
			System.out.println("Enter string containing delimiters:");
			System.out.flush();
			input=getString();
			if("".equals(input)){
				break;
			}
			BracketChecker theChecker=new BracketChecker(input);
			theChecker.check();
		}
	}
	public static String getString() throws IOException{
		InputStreamReader isr = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(isr);
		String s = br.readLine();
		return s;
	}
}

基于链表的栈

package datastructure.c5.linklist.linkstack;

public class Link {
	public long dData;
	public Link next;
	public Link(long d){
		dData=d;
	}
	public void displayLink(){
		System.out.print(dData+"  ");
	}
}

package datastructure.c5.linklist.linkstack;

public class LinkList {
	private Link first;
	public LinkList(){
		first=null;
	}
	public boolean isEmpty(){
		return first==null;
	}
	public void insertFirst(long dd){
		Link newLink=new Link(dd);
		newLink.next=first;
		first=newLink;
	}
	public long deleteFirst(){
		Link temp=first;
		first=first.next;
		return temp.dData;
	}
	public void displayList(){
		Link current=first;
		while(current!=null){
			current.displayLink();
			current=current.next;
		}
		System.out.println("");
	}
}

package datastructure.c5.linklist.linkstack;

public class LinkStack {
	private LinkList theList;
	public LinkStack(){
		theList=new LinkList();
	}
	public void push(long j){
		theList.insertFirst(j);
	}
	public long pop(){
		return theList.deleteFirst();
	}
	public boolean isEmpty(){
		return theList.isEmpty();
	}
	public void displayStack(){
		System.out.println("Stack (top-->bottom):");
		theList.displayList();
	}
}

package datastructure.c5.linklist.linkstack;

public class LinkStackApp {
	public static void main(String[] args) {
		LinkStack theStack=new LinkStack();
		theStack.push(20);
		theStack.push(40);
		theStack.displayStack();
		theStack.push(60);
		theStack.push(80);
		theStack.displayStack();
		theStack.pop();
		theStack.pop();
		theStack.displayStack();
	}
}