59、java集合-ArrayList

一、ArrayList类概述及使用1、ArrayList类概述1）底层数据结构是数组，查询快，增删慢2）线程不安全，效率高二、ArrayList案例/* * ArrayList的使用。 * 存储字符串并遍历 */public class ArrayListDemo {public static void main(String[] args) {// 创建集合对象ArrayList array = new ArrayList();// 创建元素对象，并添加元素array.add("hello");array.add("world");array.add("java");// 遍历Iterator it = array.iterator();while (it.hasNext()) {String s = (String) it.next();System.out.println(s);}System.out.println("-----------");for (int x = 0; x < array.size(); x++) {String s = (String) array.get(x);System.out.println(s);}}}/* * ArrayList存储自定义对象并遍历 */public class ArrayListDemo2 {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);Student s4 = new Student("杨志", 38);// 添加元素array.add(s1);array.add(s2);array.add(s3);array.add(s4);// 遍历Iterator it = array.iterator();while (it.hasNext()) {Student s = (Student) it.next();System.out.println(s.getName() + "---" + s.getAge());}System.out.println("----------------");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());}}}