ArrayList

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public class Student {private String name;private int age;public Student() {super();}public Student(String name, int age) {super();this.name = name;this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}}

import java.util.ArrayList;import java.util.Iterator;/* * List的子类特点： * ArrayList: * 底层数据结构是数组，查询快，增删慢 * 线程不安全，效率高 * Vector: * 底层数据结构是数组，查询快，增删慢 * 线程安全，效率低 * LinkedList: *  底层数据结构是链表，查询慢，增删快 * 线程不安全，效率高 */public class ArrayListDemo {public static void main(String[] args) {// 创建集合对象ArrayList array = new ArrayList();// 创建学生对象Student s1 = new Student("武松", 30);Student s2 = new Student("鲁智深", 40);Student s3 = new Student("林冲", 36);// 添加元素array.add(s1);array.add(s2);array.add(s3);// 遍历Iterator it = array.iterator();while (it.hasNext()) {Student s = (Student) it.next();System.out.println(s.getName() + "---" + s.getAge());}for (int x = 0; x < array.size(); x++) {// ClassCastException 注意，千万要搞清楚类型// String s = (String) array.get(x);// System.out.println(s);Student s = (Student) array.get(x);System.out.println(s.getName() + "---" + s.getAge());}}}

public class Student {private String name;private int age;public Student() {super();}public Student(String name, int age) {super();this.name = name;this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}}

import java.util.ArrayList;/* * 集合的嵌套遍历 * 需求： * 我们班有学生，每一个学生是不是一个对象。所以我们可以使用一个集合表示我们班级的学生。ArrayList<Student> * 但是呢，我们旁边是不是还有班级，每个班级是不是也是一个ArrayList<Student>。 * 而我现在有多个ArrayList<Student>。也要用集合存储，怎么办呢? * 就是这个样子的：ArrayList<ArrayList<Student>> */public class ArrayListDemo {public static void main(String[] args) {// 创建大集合ArrayList<ArrayList<Student>> bigArrayList = new ArrayList<ArrayList<Student>>();// 创建第一个班级的学生集合ArrayList<Student> firstArrayList = new ArrayList<Student>();// 创建学生Student s1 = new Student("唐僧", 30);Student s2 = new Student("孙悟空", 29);Student s3 = new Student("猪八戒", 28);Student s4 = new Student("沙僧", 27);Student s5 = new Student("白龙马", 26);// 学生进班firstArrayList.add(s1);firstArrayList.add(s2);firstArrayList.add(s3);firstArrayList.add(s4);firstArrayList.add(s5);// 把第一个班级存储到学生系统中bigArrayList.add(firstArrayList);// 创建第二个班级的学生集合ArrayList<Student> secondArrayList = new ArrayList<Student>();// 创建学生Student s11 = new Student("诸葛亮", 30);Student s22 = new Student("司马懿", 28);Student s33 = new Student("周瑜", 26);// 学生进班secondArrayList.add(s11);secondArrayList.add(s22);secondArrayList.add(s33);// 把第二个班级存储到学生系统中bigArrayList.add(secondArrayList);// 创建第三个班级的学生集合ArrayList<Student> thirdArrayList = new ArrayList<Student>();// 创建学生Student s111 = new Student("宋江", 40);Student s222 = new Student("吴用", 35);Student s333 = new Student("高俅", 30);Student s444 = new Student("李师师", 22);// 学生进班thirdArrayList.add(s111);thirdArrayList.add(s222);thirdArrayList.add(s333);thirdArrayList.add(s444);// 把第三个班级存储到学生系统中bigArrayList.add(thirdArrayList);// 遍历集合for (ArrayList<Student> array : bigArrayList) {for (Student s : array) {System.out.println(s.getName() + "---" + s.getAge());}}}}

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