commons的迭代器和双向Map——高淇JAVA300讲笔记之commons
案例一：迭代器
1 package com.bjsxt.others.commons; 2 3 import java.util.ArrayList; 4 import java.util.Iterator; 5 import java.util.List; 6 7 import org.apache.commons.collections4.IterableMap; 8 import org.apache.commons.collections4.MapIterator; 9 import org.apache.commons.collections4.Predicate; 10 import org.apache.commons.collections4.iterators.ArrayListIterator; 11 import org.apache.commons.collections4.iterators.FilterIterator; 12 import org.apache.commons.collections4.iterators.LoopingIterator; 13 import org.apache.commons.collections4.iterators.UniqueFilterIterator; 14 import org.apache.commons.collections4.map.HashedMap; 15 16 17 /** 18 * 迭代器的扩展 19 * 1、MapIterator 以后不再使用map.keySet.iterator访问 20 * IterableMap HashedMap 21 * 2、UniqueFilterIterator 去重迭代器 22 * 3、FilterIterator 自定义过滤 + Predicate 23 * 4、LoopingIterator 循环迭代器 24 * 5、ArrayListIterator 数组迭代器 25 * 26 */ 27 public class Demo06 { 28 29 public static void main(String[] args) { 30 // mapIt(); 31 // uniqueIt(); 32 // filterIt(); 33 // loopIt(); 34 arrayIt(); 35 } 36 /** 37 * 数组迭代器 38 */ 39 public static void arrayIt() { 40 System.out.println("=======数组迭代器======"); 41 int[] arr = {1,2,3,4,5}; 42 //数组迭代器 43 // Iterator<Integer> it = new ArrayListIterator<Integer>(arr); 44 //指定起始索引和结束索引 45 Iterator<Integer> it = new ArrayListIterator<Integer>(arr,1,3); 46 while(it.hasNext()) { 47 System.out.println(it.next()); 48 } 49 } 50 51 /** 52 * 循环迭代器 53 */ 54 public static void loopIt() { 55 System.out.println("=======循环迭代器======"); 56 List<String> list = new ArrayList<String>(); 57 list.add("refer"); 58 list.add("dad"); 59 list.add("bjsxt"); 60 list.add("moom"); 61 62 Iterator<String> it = new LoopingIterator(list); 63 for(int i=0;i<5;i++) { 64 System.out.println(it.next()); 65 } 66 67 } 68 69 70 /** 71 * 自定义迭代器 72 */ 73 public static void filterIt() { 74 System.out.println("=======自定义迭代器======"); 75 List<String> list = new ArrayList<String>(); 76 list.add("refer"); 77 list.add("dad"); 78 list.add("bjsxt"); 79 list.add("moom"); 80 //自定义条件判断 81 Predicate<String> pre = new Predicate<String>() { 82 @Override 83 public boolean evaluate(String value) { 84 //回文判断 85 return new StringBuilder(value).reverse().toString().equals(value); 86 } 87 }; 88 89 //过滤器 90 Iterator<String> it = new FilterIterator(list.iterator(),pre); 91 while(it.hasNext()) { 92 System.out.println(it.next()); 93 } 94 } 95 96 /** 97 * 去重迭代器 98 */ 99 public static void uniqueIt() { 100 System.out.println("=======去重迭代器======"); 101 List<String> list = new ArrayList<String>(); 102 list.add("a"); 103 list.add("b"); 104 list.add("a"); 105 //去除重复的过滤器 106 Iterator<String> it = new UniqueFilterIterator(list.iterator()); 107 while(it.hasNext()) { 108 System.out.println(it.next()); 109 } 110 } 111 112 /** 113 * map迭代器 114 */ 115 public static void mapIt() { 116 System.out.println("=======map迭代器======"); 117 IterableMap<String,String> map = new HashedMap<String,String>(); 118 map.put("a","bjsxt"); 119 map.put("b","sxt"); 120 map.put("c","good"); 121 //使用MapIterator 122 MapIterator<String,String> it = map.mapIterator(); 123 while(it.hasNext()) { 124 //一定要it.next() 125 String key = it.next(); 126 String value = it.getValue(); 127 System.out.println(key+"-->"+value); 128 129 } 130 131 } 132 133 }
案例二：有序和无序的双向Map
1 package com.bjsxt.others.commons; 2 3 import org.apache.commons.collections4.BidiMap; 4 import org.apache.commons.collections4.MapIterator; 5 import org.apache.commons.collections4.bidimap.DualHashBidiMap; 6 import org.apache.commons.collections4.bidimap.DualTreeBidiMap; 7 8 /** 9 * 双向Map 要求键与值都不能重复 10 * BidiMap inverseBidiMap() 11 * 1、DualTreeBidMap: 有序 12 * 2、DualHashBidMap: 无序 13 * 14 */ 15 public class Demo07 { 16 17 public static void main(String[] args) { 18 hashMap(); 19 treeMap(); 20 } 21 22 /** 23 * 有序的双向Map 24 */ 25 public static void treeMap() { 26 System.out.println("=======有序的双向Map======="); 27 BidiMap<String,String> map = new DualTreeBidiMap<String,String>(); 28 map.put("bj", "bj@test.com"); 29 map.put("sxt", "sxt@qq.com"); 30 31 //遍历查看 32 MapIterator<String,String> it = map.inverseBidiMap().mapIterator(); 33 while(it.hasNext()) { 34 String key = it.next(); 35 String value = it.getValue(); 36 System.out.println(key+"-->"+value); 37 } 38 } 39 40 /** 41 * 无序的双向Map 42 */ 43 public static void hashMap() { 44 System.out.println("=======无序的双向Map======="); 45 BidiMap<String,String> map = new DualHashBidiMap<String,String>(); 46 map.put("bj", "bj@test.com"); 47 map.put("sxt", "sxt@qq.com"); 48 //反转 49 System.out.println(map.inverseBidiMap().get("sxt@qq.com")); 50 //遍历查看 51 MapIterator<String,String> it = map.inverseBidiMap().mapIterator(); 52 while(it.hasNext()) { 53 String key = it.next(); 54 String value = it.getValue(); 55 System.out.println(key+"-->"+value); 56 } 57 } 58 59 }
运行结果：
=======无序的双向Map======= sxt bj@test.com-->bj sxt@qq.com-->sxt =======有序的双向Map======= bj@test.com-->bj sxt@qq.com-->sxt
案例三：Bag 包
1 package com.bjsxt.others.commons; 2 3 import java.util.Iterator; 4 import java.util.Set; 5 6 import org.apache.commons.collections4.Bag; 7 import org.apache.commons.collections4.bag.HashBag; 8 import org.apache.commons.collections4.bag.TreeBag; 9 10 /** 11 * Bag 包 允许重复 12 * 1、HashBag 无序 13 * 2、TreeBag 无序 14 * 统计单词的出现次数 15 * 16 */ 17 public class Demo08 { 18 public static void main(String[] args) { 19 hashBag(); 20 treeBag(); 21 String str = "this is a cat and that is a mice where is the food"; 22 //分割字符串 23 String[] strArray = str.split(" "); 24 Bag<String> bag = new TreeBag<String>(); 25 for(String temp:strArray) { 26 bag.add(temp); 27 } 28 29 System.out.println("========统计次数======"); 30 Set<String> keys = bag.uniqueSet(); 31 for(String letter:keys) { 32 System.out.println(letter+"-->"+bag.getCount(letter)); 33 } 34 35 } 36 /** 37 * 有序 38 */ 39 public static void treeBag() { 40 System.out.println("======有序的包======="); 41 Bag<String> bag = new TreeBag<String>(); 42 bag.add("a"); 43 bag.add("a",5); 44 bag.remove("a",2); 45 bag.add("b"); 46 bag.add("c"); 47 48 Iterator<String> it = bag.iterator(); 49 while(it.hasNext()) { 50 System.out.println(it.next()); 51 } 52 } 53 /** 54 * 无序 55 */ 56 public static void hashBag() { 57 System.out.println("======无序的包======="); 58 Bag<String> bag = new HashBag<String>(); 59 bag.add("a"); 60 bag.add("a",5); 61 bag.remove("a",2); 62 bag.add("b"); 63 bag.add("c"); 64 65 Iterator<String> it = bag.iterator(); 66 while(it.hasNext()) { 67 System.out.println(it.next()); 68 } 69 } 70 }
运行结果：
======无序的包======= a a a a b c ======有序的包======= a a a a b c ========统计次数====== a-->2 and-->1 cat-->1 food-->1 is-->3 mice-->1 that-->1 the-->1 this-->1 where-->1
