遍历Map的3种方法
集合的一个很重要的操作---遍历，学习了三种遍历方法，三种方法各有优缺点~~
package cn.tsp2c.liubao;import java.util.Collection;import java.util.HashMap;import java.util.Iterator;import java.util.Map;import java.util.Set;import java.util.TreeMap;public class TestMap { public static void main(String[] args) { Map<String, Student> map = new HashMap<String, Student>(); Student s1 = new Student("宋江", "1001", 38); Student s2 = new Student("卢俊义", "1002", 35); Student s3 = new Student("吴用", "1003", 34); map.put("1001", s1); map.put("1002", s2); map.put("1003", s3); Map<String, Student> subMap = new HashMap<String, Student>(); subMap.put("1008", new Student("tom", "1008", 12)); subMap.put("1009", new Student("jerry", "1009", 10)); map.putAll(subMap); work(map); workByKeySet(map); workByEntry(map); } [color=red]最常规的一种遍历方法，最常规就是最常用的，虽然不复杂，但很重要，这是我们最熟悉的，就不多说了！！[/color] public static void work(Map<String, Student> map) { Collection<Student> c = map.values(); Iterator it = c.iterator(); for (; it.hasNext();) { System.out.println(it.next()); } } [color=red]利用keyset进行遍历，它的优点在于可以根据你所想要的key值得到你想要的 values，更具灵活性！！[/color] public static void workByKeySet(Map<String, Student> map) { Set<String> key = map.keySet(); for (Iterator it = key.iterator(); it.hasNext();) { String s = (String) it.next(); System.out.println(map.get(s)); } } [color=red]比较复杂的一种遍历在这里，呵呵~~他很暴力哦，它的灵活性太强了，想得到什么就能得到什么~~[/color] public static void workByEntry(Map<String, Student> map) { Set<Map.Entry<String, Student>> set = map.entrySet(); for (Iterator<Map.Entry<String, Student>> it = set.iterator(); it.hasNext();) { Map.Entry<String, Student> entry = (Map.Entry<String, Student>) it.next(); System.out.println(entry.getKey() + "--->" + entry.getValue()); } }}class Student { private String name; private String id; private int age; public Student(String name, String id, int age) { this.name = name; this.id = id; this.age = age; } @Override public String toString() { return "Student{" + "name=" + name + "id=" + id + "age=" + age + '}'; }}