四种Map集合的遍历方式

package a0827;

import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;

import org.junit.Test;

public class testMap {

	/**
	 * @param args
	 */
	@Test
	public void keySet() {
		// 定义并初始化map
		Map map = new LinkedHashMap<String, String>();
		map.put("1", "aaa");
		map.put("2", "bbb");
		map.put("3", "ccc");

		// 通过keyset和迭代器方式获取并输出map元素
		Set set = map.keySet();
		Iterator it = set.iterator();
		while (it.hasNext()) {
			String key = (String) it.next();
			String value = (String) map.get(key);
			System.out.println("key:" + key + "\t" + "value:" + value);
		}
	}

	@Test
	public void forKeySet() {
		// 定义并初始化map
		Map map = new LinkedHashMap<String, String>();
		map.put("1", "aaa");
		map.put("2", "bbb");
		map.put("3", "ccc");

		// 通过keyset和增强for循环的方式获取并输出map元素
		for (Object obj : map.keySet()) {
			String key = (String) obj;
			String value = (String) map.get(key);
			System.out.println("key:" + key + "\t" + "value:" + value);
		}
	}

	@Test
	public void entrySet() {
		// 定义并初始化map
		Map map = new LinkedHashMap<String, String>();
		map.put("1", "aaa");
		map.put("2", "bbb");
		map.put("3", "ccc");

		// 通过keyset和迭代器方式获取并输出map元素
		Set set = map.entrySet();
		Iterator it = set.iterator();
		while (it.hasNext()) {
			Map.Entry entry = (Map.Entry) it.next();
			String key = (String) entry.getKey();
			String value = (String) entry.getValue();
			System.out.println("key:" + key + "\t" + "value:" + value);
		}
	}

	@Test
	public void forEntrySet() {
		// 定义并初始化map
		Map map = new LinkedHashMap<String, String>();
		map.put("1", "aaa");
		map.put("2", "bbb");
		map.put("3", "ccc");

		// 通过keyset和迭代器方式获取并输出map元素
		for (Object obj : map.entrySet()) {
			Map.Entry entry = (Map.Entry) obj;
			String key = (String) entry.getKey();
			String value = (String) entry.getValue();
			System.out.println("key:" + key + "\t" + "value:" + value);
		}
	}
}