java 遍历Map及Map转化为二维数组的实例

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<String, String> map1 = new HashMap<String, String>(); 
    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<String, String> map2 = new HashMap<String, String>(); 
    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<Map.Entry<String, String>> iterator = map2.entrySet().iterator();  
    String[][] group2 = new String[map2.size()][2]; 
    while (iterator.hasNext()) {  
      Map.Entry<String, String> 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<String, String> map = new HashMap<String, String>(); 
    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<String, String> 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]);  
    } 
     
  } 
} 

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