如何遍历Map及将Map转化为二维数组

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class Test {
	public static void main(String[] args) {
		int a = 0, b = 0, c = 0;
		// 第一种:通过Map.keySet()遍历Map及将Map转化为二维数组
		Map map1 = new HashMap();
		map1.put("012013012013", "张三");
		map1.put("012013012014", "张四");
		String[][] group1 = new String[map1.size()][2];
		System.out.println("第一种:通过Map.keySet()遍历map1的key和value");
		for (String key : map1.keySet()) {  
	    	System.out.println("key = " + key + " and value = " + map1.get(key));  
	    	group1[a][0] = key;
	    	group1[a][1] = map1.get(key);
	    	a++;
	    } 
		System.out.println("map1.size()为：" + map1.size() + ",a为：" + a + "，group1数组的长度为：" + group1.length);
		System.out.println("----------------------------------------------------");
		for(int n = 0; n < group1.length; n++) {
			System.out.println("key = " + group1[n][0] + " and value = " + group1[n][1]);  
		}
		
		// 第二种:通过Map.entrySet()使用iterator()遍历Map及将Map转化为二维数组
		Map map2 = new HashMap();
		map2.put("112013012013", "李三");
		map2.put("112013012014", "李四");
		System.out.println("\n" + "第二种:通过Map.entrySet()使用iterator()遍历map2的key和value");
		Iterator> iterator = map2.entrySet().iterator();  
		String[][] group2 = new String[map2.size()][2];
        while (iterator.hasNext()) {  
            Map.Entry entry = iterator.next();                
            System.out.println("key = " + entry.getKey() + " and value = " + entry.getValue());
            group2[b][0] = entry.getKey();
	    	group2[b][1] = entry.getValue();
	    	b++;
        }  
        System.out.println("map2.size()为：" + map2.size() + ",b为：" + b + "，group2数组的长度为：" + group2.length);
        System.out.println("----------------------------------------------------");
        for(int n = 0; n < group2.length; n++) {
			System.out.println("key = " + group2[n][0] + " and value = " + group2[n][1]);  
		}
        
        // 第三种:通过Map.entrySet()遍历遍历Map及将Map转化为二维数组
        Map map = new HashMap();
		map.putAll(map1);
		map.putAll(map2);	
		String[][] group3 = new String[map.size()][2];
		System.out.println("\n" + "第三种:通过Map.entrySet()遍历map的key和value ");		
		for (Map.Entry entry : map.entrySet()) {  
            System.out.println("key = " + entry.getKey() + " and value = " + entry.getValue()); 
            group3[c][0] = entry.getKey();
	    	group3[c][1] = entry.getValue();
	    	c++;
        }
		System.out.println("map.size()为：" + map.size() + ",c为：" + c + "，group3数组的长度为：" + group3.length);
		System.out.println("----------------------------------------------------");
	    for(int n = 0; n < group3.length; n++) {
			System.out.println("key = " + group3[n][0] + " and value = " + group3[n][1]);  
		}
		
	}
}

输出结果为：

第一种:通过Map.keySet()遍历map1的key和value
key = 012013012013 and value = 张三
key = 012013012014 and value = 张四
map1.size()为：2,a为：2，group1数组的长度为：2
----------------------------------------------------
key = 012013012013 and value = 张三
key = 012013012014 and value = 张四

第二种:通过Map.entrySet()使用iterator()遍历map2的key和value
key = 112013012014 and value = 李四
key = 112013012013 and value = 李三
map2.size()为：2,b为：2，group2数组的长度为：2
----------------------------------------------------
key = 112013012014 and value = 李四
key = 112013012013 and value = 李三

第三种:通过Map.entrySet()遍历map的key和value 
key = 112013012014 and value = 李四
key = 112013012013 and value = 李三
key = 012013012013 and value = 张三
key = 012013012014 and value = 张四
map.size()为：4,c为：4，group3数组的长度为：4
----------------------------------------------------
key = 112013012014 and value = 李四
key = 112013012013 and value = 李三
key = 012013012013 and value = 张三
key = 012013012014 and value = 张四