感谢Java软件结构与数据结构 John Lewis Joseph chase 著 金名译
0. 迭代器关键概念（补充理解）
【1】迭代器是一个对象，它提供了一种依次访问集合中每个元素的方式。
【2】经常把集合定义为Iterable的，说明需要时可以提供一个迭代器。
【3】迭代器可选方法remove使得它可以remove一个元素，而无需再遍历集合。
【4】大多数迭代器是fail-fast的，当迭代器人在使用之时，如果修改集合，将抛出一个异常。
【5】不能假设迭代器访问元素的顺序，除非显式声明。
【6】迭代器往往实现为它所属的集合的内部类。
【7】迭代器检查修改技术，以确保与集合的修改计数保持一致。
【8】for-each循环只能够用于实现了iterator接口的集合中，
【9】如果不是要处理集合中的所有元素或者如果要使用迭代器的remove方法，可以使用显式迭代器而不是for-each循环。
【10】如果底层集合不是由迭代器本身进行修改的，fail-fast迭代器将快速而清晰地发生失败。
【11】fail-fast的实现：在后继的操作中，迭代器会通知集合的修改计数，确保该值不会被修改。如果改了，迭代器就会抛出ConcurrentModificationException异常。
2. Java集合API列表
Java集合API提供的列表类主要是支持索引列表。在一定程度上，这些类同无序列表是重叠的。JavaAPI中没有实现事实上的有序列表。
【1】ArrayList是实现了基于动态数组的数据结构，LinkedList基于链表的数据结构。
【2】对于随机访问get和set，ArrayList觉得优于LinkedList，因为LinkedList要移动指针。
【3】对于新增和删除操作add和remove，LinedList比较占优势，因为ArrayList要移动数据。
ArrayList和LinkedList都实现了java.util.List接口。
3. 使用无序列表：学习计划
Course.java
package ds.java.ch06;import java.io.Serializable;/** * @author LbZhang* @version 创建时间：2015年11月18日 上午10:19:57 * @description 类说明*/
public class Course implements Serializable{private String prefix;private int number;private String title;private String grade;public Course(String prefix, int number, String title, String grade) {super();this.prefix = prefix;this.number = number;this.title = title;if(grade==null){this.grade = "";}else{this.grade = grade;}}public Course(String prefix, int number, String title){this(prefix, number, title, "");}public String getPrefix() {return prefix;}public void setPrefix(String prefix) {this.prefix = prefix;}public int getNumber() {return number;}public void setNumber(int number) {this.number = number;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getGrade() {return grade;}public void setGrade(String grade) {this.grade = grade;}/*** Returns true if this course has been taken * * @return true if this course has been taken and false otherwise*/public boolean taken(){return !grade.equals("");}public boolean equals(Object other){boolean result = false;if (other instanceof Course){Course otherCourse = (Course) other;if (prefix.equals(otherCourse.getPrefix()) &&number == otherCourse.getNumber())result = true;}return result;}public String toString(){String result = prefix + " " + number + ": " + title;if (!grade.equals(""))result += " [" + grade + "]";return result;}}
ProgramOfStudy.java
package ds.java.ch06;import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;/*** @author LbZhang* @version 创建时间：2015年11月17日 上午11:30:41* @description 类说明*/
public class ProgramOfStudy implements Iterable<Course>, Serializable {private List<Course> list;public ProgramOfStudy() {list = new LinkedList<Course>();}public void addCourse(Course course) {if (course != null)list.add(course);}public Course find(String prefix, int number) {for (Course course : list)if (prefix.equals(course.getPrefix())&& number == course.getNumber())return course;return null;}/*** 在某个元素之后添加元素* @param target* @param newCourse*/public void addCourseAfter(Course target, Course newCourse) {if (target == null || newCourse == null)return;int targetIndex = list.indexOf(target);//获取索引if (targetIndex != -1)list.add(targetIndex + 1, newCourse);}public void replace(Course target, Course newCourse) {if (target == null || newCourse == null)return;int targetIndex = list.indexOf(target);if (targetIndex != -1)list.set(targetIndex, newCourse);}public String toString() {String result = "";for (Course course : list)result += course + "\n";return result;}public Iterator<Course> iterator() {return list.iterator();}public void save(String fileName) throws IOException {FileOutputStream fos = new FileOutputStream(fileName);ObjectOutputStream oos = new ObjectOutputStream(fos);oos.writeObject(this);oos.flush();oos.close();}public static ProgramOfStudy load(String fileName) throws IOException,ClassNotFoundException {FileInputStream fis = new FileInputStream(fileName);ObjectInputStream ois = new ObjectInputStream(fis);ProgramOfStudy pos = (ProgramOfStudy) ois.readObject();System.out.println(pos);ois.close();return pos;}}
POSTester.java
package ds.java.ch06;
import java.io.IOException;/*** @author LbZhang* @version 创建时间：2015年11月18日 上午9:46:48* @description 类说明*/
public class POSTester {public static void main(String[] args) throws IOException,ClassNotFoundException {ProgramOfStudy pos = new ProgramOfStudy();pos.addCourse(new Course("CS", 101, "Introduction to Programming", "A-"));pos.addCourse(new Course("ARCH", 305, "Building Analysis", "A"));pos.addCourse(new Course("GER", 210, "Intermediate German"));pos.addCourse(new Course("CS", 320, "Computer Architecture"));pos.addCourse(new Course("THE", 201, "The Theatre Experience"));Course arch = pos.find("CS", 320);pos.addCourseAfter(arch, new Course("CS", 321, "Operating Systems"));Course theatre = pos.find("THE", 201);theatre.setGrade("A-");Course german = pos.find("GER", 210);pos.replace(german, new Course("FRE", 110, "Beginning French", "B+"));System.out.println(pos);pos.save("ProgramOfStudy");
// pos = pos.load("ProgramOfStudy");
// System.out.println(pos);}}
4. 约瑟夫问题
4.1 索引列表实现
package ds.java.ch06;import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;/*** @author LbZhang* @version 创建时间：2015年11月18日 上午11:18:20* @description 约瑟夫问题* */
public class Josephus {public static void main(String[] args) {int numPeople, skip, targetIndex;List<String> list = new ArrayList<String>();Scanner in = new Scanner(System.in);// get the initial number of soldiersSystem.out.print("Enter the number of soldiers: ");numPeople = in.nextInt();in.nextLine();// get the number of soldiers to skipSystem.out.print("Enter the number of soldiers to skip: ");skip = in.nextInt();if(numPeople<skip){System.out.println("**不能进行约瑟夫环**");return ;}// load the initial list of soldiersfor (int count = 1; count <= numPeople; count++) {list.add("Soldier " + count);}//now location indextargetIndex = skip;System.out.println("The order is: ");// Treating the list as circular, remove every nth element// until the list is emptywhile (list.size()>2) {System.out.println(list.remove(targetIndex));if (list.size() > 0)targetIndex = (targetIndex + skip) % list.size();}System.out.println(list);}}
4.2 数组实现
package ds.java.ch06;import java.util.Scanner;/*** @author LbZhang* @version 创建时间：2015年11月18日 下午12:23:55* @description 类说明*/
public class MyJosephus {private int total;// 总人数private int numCount;// 从当前开始第几个出列private int beginNum;// 开始编号private int[] solider;// 士兵队列private int[] outSequence;// 出队次序public MyJosephus(int total, int numCount, int beginNum) {super();this.total = total;this.numCount = numCount;this.beginNum = beginNum;this.solider = new int[total];// 初始化for (int i = 0; i < solider.length; i++) {solider[i] = i;}this.outSequence = new int[total];}public void exec() {int counter = 0;// /标价变量int i = this.beginNum;int j = 0;int killperson = 0;while (true) {if (solider[i] != -1) {// pserson[i]的值是-1，代表出环// 没有出环，计数器加1counter++;// 判定是否数目达到numCountif ((counter) % numCount == 0) {outSequence[j++] = i + 1;// 填入队列killperson++;solider[i] = -1;// 杀死当前编号士兵}}i = (i + 1) % total;// 向后遍历if (killperson == total) {break;}}System.out.println("出环按顺序为：");for (int k = 0; k < outSequence.length; k++) {// 输出出环顺序System.out.print(outSequence[k] + " ");}}public static void main(String[] args) {int total = 0;int numCount = 0;int begin = 0;Scanner scn = new Scanner(System.in);while (true) {System.out.println("Input total num:");total = scn.nextInt();System.out.println("Input numCount:");numCount = scn.nextInt();System.out.println("Input begin:");begin = scn.nextInt();if (total != 0 && numCount != 0 && total > numCount) {MyJosephus mj = new MyJosephus(total, numCount, begin);mj.exec();break;} else {System.out.println("您输入的数据不合理，请重试！");}}}}
输出结果：
![地理信息科学前沿-[热词]](https://img-blog.csdn.net/20160505182455312?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQv/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center)
