特點：先入先出(類似于銀行排隊問題)

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一、數組模擬隊列

package com.company;import java.util.Scanner;/*** @author:抱著魚睡覺的喵喵* @date:2021/1/31* @description: the array simulate the queue*/ public class ArrayQueue {//test array simulate queuepublic static void main(String[] args) {ArraySimulateQueue arraySimulateQueue = new ArraySimulateQueue(3);char key=' ';Scanner scanner = new Scanner(System.in);boolean flag=true;while (flag){System.out.println("s:show queue");System.out.println("a:add data to the queue");System.out.println("g:the data obtained from the queue");System.out.println("h:view queue header data");System.out.println("e:exit the program");key=scanner.next().charAt(0);switch (key){case 's':arraySimulateQueue.showQueue();break;case 'a':System.out.println("please entry a data!");int data=scanner.nextInt();arraySimulateQueue.enQueue(data);break;case 'g':try {int result=arraySimulateQueue.deQueue();System.out.println("the data obtained from the queue is:"+result);}catch (Exception e){System.out.println(e.getMessage());}break;case 'h':try {int frontData=arraySimulateQueue.getFront();System.out.println("the head of the queue data is:"+frontData);}catch (Exception e){System.out.println(e.getMessage());}break;case 'e':scanner.close();flag=false;return;default:System.out.println("the characters you entered are wrong!");}}System.out.println("program has exited!");} } /*** use array to simulate queue*/ class ArraySimulateQueue{private int maxSize;private int front;private int rear;private int[] arr;public ArraySimulateQueue(int currentMaxSize){this.maxSize=currentMaxSize;this.front=-1;this.rear=-1;arr=new int[maxSize];}//determine whether the queue is fullpublic boolean isFull(){return rear == maxSize-1;}//determine whether the queue is emptypublic boolean isEmpty(){return rear == front;}//enqueuepublic void enQueue(int data){if (isFull()){System.out.println("the queue is full and cannot add data!");return;}else{this.rear++;arr[rear]=data;System.out.println("successful data entry!");}}//dequeuepublic int deQueue(){if (isEmpty()){throw new RuntimeException("the queue is empty and cannot get data!");}else{this.front++;int result=arr[front];arr[front]=0;return result;}}//show datapublic void showQueue(){for (int i = 0; i < arr.length; i++) {System.out.printf("arr[%d]=%d",i,arr[i]);;System.out.println();}}public int getFront(){if (isEmpty()){throw new RuntimeException("the queue is empty and cannot get header data!");}else{return arr[front+1];}} }

分析缺點：

由圖可以看出使用過的內存單元將不能夠繼續使用，所以使用環形隊列可以解決內存資源浪費的問題

環形隊列

實現方式1

package com.company;import java.util.Scanner;/*** @author:抱著魚睡覺的喵喵* @date:2021/2/1* @description: the array simulate the circular queue*/ public class CircleArrayQueue {public static void main(String[] args) {CircleQueue circleQueue = new CircleQueue(3);boolean flag = true;Scanner scanner = new Scanner(System.in);char key = ' ';while (flag) {System.out.println("s:show queue");System.out.println("a:add data to the queue");System.out.println("g:get data from the queue");System.out.println("h:view queue header data");System.out.println("e:exit the program");key = scanner.next().charAt(0);switch (key) {case 's':circleQueue.showData();break;case 'a':System.out.println("please enter a data:");int result = scanner.nextInt();circleQueue.enQueue(result);break;case 'g':try {System.out.printf("the data obtained from queue is:%d", circleQueue.dequeue());System.out.println();} catch (Exception e) {System.out.println(e.getMessage());}break;case 'h':try {System.out.printf("header data is:%d", circleQueue.getFront());System.out.println();} catch (Exception e) {System.out.println(e.getMessage());}break;case 'e':scanner.close();flag = false;}}} }/*** Circular simulate queue*/ class CircleQueue {private int maxSize;private int front;private int rear;private int[] arr;private int num;public CircleQueue(int currentMaxSize) {this.maxSize = currentMaxSize;this.front = -1;this.rear = -1;arr = new int[maxSize];this.num = 0; //record the number of array units and used to determine whether the circular queue is full or empty}//determine whether the circular queue is fullpublic boolean isFull() {return num == maxSize;}//determine whether the circular queue is emptypublic boolean isEmpty() {return num == 0;}//enqueuepublic void enQueue(int data) {if (isFull()) {System.out.println("the circular is full,unable to add data!");} else if ((rear + 1 == maxSize) && (!isFull())) {rear = 0;arr[rear] = data;num++;} else {rear++;arr[rear] = data;num++;}}//dequeuepublic int dequeue() {if (isEmpty()) {throw new RuntimeException("the circular queue is empty,unable to leave the queue!");} else if ((front + 1 == maxSize) && (!isEmpty())) {front = 0;int result = arr[front];arr[front] = 0;num--;return result;} else {front++;int result = arr[front];arr[front] = 0;num--;return result;}}//get the circular queue header datapublic int getFront() {if (isEmpty()) {throw new RuntimeException("the circular queue is empty cannot get header data!");} else if (front +1 == maxSize){return arr[0];} else {return arr[front+1];}}//show datapublic void showData() {for (int i = 0; i < arr.length; i++) {System.out.printf("arr[%d]=%d", i, arr[i]);System.out.println();}} }

實現方式2

package com.company;import java.util.Scanner;/*** @author:抱著魚睡覺的喵喵* @date:2021/2/2* @description:*/ public class CircleArrayQueue2 {public static void main(String[] args) {CircleQueue2 circleQueue = new CircleQueue2(3);boolean flag = true;Scanner scanner = new Scanner(System.in);char key = ' ';while (flag) {System.out.println("s:show queue");System.out.println("a:add data to the queue");System.out.println("g:get data from the queue");System.out.println("h:view queue header data");System.out.println("e:exit the program");key = scanner.next().charAt(0);switch (key) {case 's':circleQueue.showData();break;case 'a':System.out.println("please enter a data:");int result = scanner.nextInt();circleQueue.enQueue(result);break;case 'g':try {System.out.printf("the data obtained from queue is:%d", circleQueue.dequeue());System.out.println();} catch (Exception e) {System.out.println(e.getMessage());}break;case 'h':try {System.out.printf("header data is:%d", circleQueue.getFront());System.out.println();} catch (Exception e) {System.out.println(e.getMessage());}break;case 'e':scanner.close();flag = false;}}} }/*** Circular simulate queue*/ class CircleQueue2 {private int maxSize;private int front;private int rear;private int[] arr;public CircleQueue2(int currentMaxSize) {this.maxSize = currentMaxSize;this.front = 0;this.rear = 0;arr = new int[maxSize];}//determine whether the circular queue is fullpublic boolean isFull() {return (rear + 1) % maxSize == front;}//determine whether the circular queue is emptypublic boolean isEmpty() {return rear == front;}//enqueuepublic void enQueue(int data) {if (isFull()) {System.out.println("the circular is full,unable to add data!");} else {arr[rear] = data;rear = (rear + 1) % maxSize;}}//dequeuepublic int dequeue() {if (isEmpty()) {throw new RuntimeException("the circular queue is empty,unable to leave the queue!");} else {int result = arr[front];arr[front] = 0;front = (front + 1) % maxSize;return result;}}//get the circular queue header datapublic int getFront() {if (isEmpty()) {throw new RuntimeException("the circular queue is empty cannot get header data!");} else {return arr[front % maxSize];}}//show datapublic void showData() {for (int i = 0; i < arr.length; i++) {System.out.printf("arr[%d]=%d", i, arr[i]);System.out.println();}} }

總結

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