import java.util.*; public class AugrumentDemo { public static void main(String[] args) { Map<String,String> map = new HashMap<String,String>(); map.put("m1","hello1"); map.put("m2","hello2"); map.put("m3","hello3"); map.put("m4","hello4"); map.put("m5","hello5"); //常用的遍历方式1 便利map 一般先变成set类型集合 然后迭代输出 Set<Map.Entry<String, String>> set = map.entrySet(); Iterator<Map.Entry<String, String>> iterator = set.iterator(); while (iterator.hasNext()){ System.out.println(iterator.next()); } System.out.println("==============================="); //遍历2 Set<String> keys = map.keySet(); //获取所有的键组成的set集合 Iterator<String> key = keys.iterator(); //迭代 或者 增强for while (key.hasNext()){ String k = key.next(); String s = map.get(k); //根据键获取对应的值 System.out.println(s); } } }
重点理解的内容:
Map.Entry<K,V>:在Map接口中有一个内部的接口Entry (类似与内部类)
作用:当Map集合一创建,那么就会在Map集合中创建一个Entry对象,用来记录键与值(键值对对象)
Set<Map.Entry<String, String>> eset = map.entrySet(); Iterator<Map.Entry<String, String>> it = eset.iterator(); while (it.hasNext()){ Map.Entry<String, String> n = it.next(); System.out.println(n.getKey()); //entry中可以直接获取键 或值 System.out.println(n.getValue()); }
hashTable