A:Collections类概述: 针对集合操作 的工具类 B:Collections成员方法 public static void sort(List list): 排序,默认按照自然顺序 public static int binarySearch(List list,T key): 二分查找 public static T max(Collection coll): 获取最大值 public static void reverse(List list): 反转 public static void shuffle(List list): 随机置换 C:案例演示: Collections工具类的常见方法讲解
案例：
import java.util.ArrayList;import java.util.Collection;import java.util.Collections;import java.util.Comparator;public class MyTest2 {public static void main(String[] args) {// Collection Set List// A:// Collections类概述:// 针对集合操作 的工具类// B:// Collections成员方法// public static void sort (List < T > list):排序, 默认按照自然顺序// public static int binarySearch (List < ? > list, T key):二分查找// public static T max(Collection < ? > coll):获取最大值// public static void reverse (List < ? > list):反转// public static void shuffle (List < ? > list):随机置换ArrayList list = new ArrayList();list.add(100);list.add(1002);list.add(1030);list.add(1050);list.add(100);//list.sort();Collections.sort(list);//Collections.sort(list, new Comparator() {//@Override//public int compare(Integer o1, Integer o2) {//return 0;//}//});//System.out.println(list);int i = Collections.binarySearch(list, 1050);System.out.println(i);System.out.println(Collections.max(list));System.out.println(Collections.min(list));Collections.reverse(list);//反转集合中的元素System.out.println(list);Collections.shuffle(list);//随机打乱集合中元素的顺序System.out.println(list);}} 模拟斗地主洗牌和发牌//A: //案例演示: //模拟斗地主洗牌和发牌，牌没有排序 //得有一副牌 案例：
import java.util.ArrayList;import java.util.Collections;public class MyTest {public static void main(String[] args) {//A://案例演示://模拟斗地主洗牌和发牌，牌没有排序//得有一副牌ArrayList pokerBox = new ArrayList();//生成54张牌放到牌盒里面String[] colors = {"♠", "♥", "♦", "♣"};String[] nums = {"A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K"};for (String color : colors) {for (String num : nums) {pokerBox.add(color.concat(num));}}//手动添加大小王pokerBox.add("★");pokerBox.add("☆");//洗牌Collections.shuffle(pokerBox);Collections.shuffle(pokerBox);Collections.shuffle(pokerBox);//发牌ArrayList 高进 = new ArrayList();ArrayList 刀仔 = new ArrayList();ArrayList 星仔 = new ArrayList();ArrayList 底牌 = new ArrayList();// 高进 = (ArrayList) pokerBox.subList(0,17);// 高进 0 3 6 9//刀仔 1 4 7 10// 星仔 2 5 8 11for (int i = 0; i < pokerBox.size(); i++) {if (i >= pokerBox.size() - 3) {底牌.add(pokerBox.get(i));} else if (i % 3 == 0) {高进.add(pokerBox.get(i));} else if (i % 3 == 1) {刀仔.add(pokerBox.get(i));} else {星仔.add(pokerBox.get(i));}}//看牌lookPoker("高进",高进);lookPoker("刀仔", 刀仔);lookPoker("星仔", 星仔);lookPoker("底牌", 底牌);}private static void lookPoker(String name, ArrayList list) {System.out.println(name);for (String s : list) {System.out.print(s+"");}System.out.println();}}结果： 高进 ♦K ♣6 ♠3 ♥8 ♥2 ♥3 ♣10 ♥K ♦6 ♣8 ♠7 ♣3 ♠K ♣7 ♦4 ♥9 ♦7 刀仔 ♦8 ♠J ★ ♥Q ♦Q ♥4 ☆ ♥5 ♠9 ♦5 ♣9 ♣Q ♠5 ♠4 ♥10 ♦A ♥J 星仔 ♠A ♦2 ♦9 ♣5 ♣J ♦3 ♦10 ♥6 ♠2 ♦J ♣2 ♥7 ♣4 ♣K ♠Q ♠10 ♠8 底牌 ♥A ♠6 ♣A
