1.直接獲取該TreeMap集合中的關係:
entrySet()java
Map接口中的方法,返回值類型是該集合中的各個關係;返回值類型是:Set類型的Map.EntrySet類型;而後在經過Set集合中特有的元素取出方式:將集合中的各個元素迭代取出;
例子:this
1 import java.util.*; 2 class MapDemo{ 3 pulbic static void main(String args[]){ 4 TreeMap<String,String> tr=new TreeMap<String,String>(); 5 tr.put("asdfda","asdfd"); 6 tr.put("asdfda","asdfd"); 7 tr.put("asdfda","asdfd"); 8 tr.put("asdfda","asdfd"); 9 Set<Map.EntrySet<String,String>> entryset=tr.entrySet(); 10 //將TreeSet中的各個映射關係經過他自身提供的方法(entrySet())轉存到Set集合中,目的是爲了使用Set集合中迭代器取出方法 11 Iterator<Map.Entry<String,String>> it=entryset.iterator();//新建一個迭代器,準備遍歷整個Set<Map.EntrySet<String,String>>集合; 12 while(it.hasNext()){ 13 Map.Entry<String,String> en=it.next();// 14 System.out.println(en.getKey()+":"+en.getValue());//在迭代每個元素的同時,同時調用Map.Entry中的方法分別獲取鍵和值 15 } 16 } 17 }
2.首先得到TreeSet集合中的全部的建(keySet()方法),而後在經過每一個建得到各個建所對應的值spa
1 import java.util.*; 2 class MapDemo4{ 3 pulbic static void main(String args[]){ 4 TreeMap<String,String> tr=new TreeMap<String,String>(); 5 tr.put("luwenxiang0","123"); 6 tr.put("luwenxiang1","123"); 7 tr.put("luwenxiang2","123"); 8 tr.put("luwenxiang3","123"); 9 tr.put("luwenxiang4","123"); 10 Set<String> arr=tr.keySet(); 11 Iterator<String> it=arr.iterator(); 12 while(it.hasNext()){ 13 String str=it.next(); 14 System.out.println(str+"::"+tr.get(str)); 15 } 16 } 17 }
3.將map轉化爲集合code
1 package com.Champter15; 2 3 import java.util.Collection; 4 import java.util.Iterator; 5 import java.util.Set; 6 import java.util.TreeMap; 7 8 class UDiskPrice implements Comparable<UDiskPrice>{ 9 int price; 10 public UDiskPrice(int price){ 11 this.price = price; 12 } 13 public int compareTo(UDiskPrice uDiskPrice){ 14 if(this.price-uDiskPrice.price==0) return 1; 15 else return this.price-uDiskPrice.price; 16 } 17 } 18 19 class UDiskCapacity implements Comparable<UDiskCapacity>{ 20 int capacity; 21 public UDiskCapacity(int capacity){ 22 this.capacity = capacity; 23 } 24 public int compareTo(UDiskCapacity uDiskCapacity){ 25 if(this.capacity-uDiskCapacity.capacity==0) return 1; 26 else return this.capacity-uDiskCapacity.capacity; 27 } 28 } 29 30 public class Work3_3 { 31 public static void main(String[] args) { 32 TreeMap<UDiskPrice,UDiskCapacity> uDiskTreeMap = new TreeMap<>(); 33 uDiskTreeMap.put(new UDiskPrice(22),new UDiskCapacity(16)); 34 uDiskTreeMap.put(new UDiskPrice(11),new UDiskCapacity(8)); 35 uDiskTreeMap.put(new UDiskPrice(33),new UDiskCapacity(64)); 36 uDiskTreeMap.put(new UDiskPrice(55),new UDiskCapacity(256)); 37 uDiskTreeMap.put(new UDiskPrice(44),new UDiskCapacity(128)); 38 39 Collection<UDiskCapacity> collection = uDiskTreeMap.values();//因爲map沒有迭代器,將映射的值存到集合中 40 Iterator<UDiskCapacity> iterator = collection.iterator();//使用集合才自帶的迭代器訪問值,值的類型爲UDiskCapacity 41 while (iterator.hasNext()){ 42 UDiskCapacity uDiskCapacity = iterator.next();//使用UDiskCapacity類型聲明的對象變量接收 43 System.out.println("按照價格升序的U盤容量:"+uDiskCapacity.capacity); 44 } }