关于Java中的一些遍历

知识分享刚起步，愿意分享工作中遇到的一些问题

Java中遍历问题

1.java中List<Map<String,Object>>遍历的方法

    List<Map<String, Object>> listMaps = new ArrayList<Map<String, Object>>();
    for (Map<String, Object> map : listMaps) {
                for (String s : map.keySet()) {
                    System.out.print(map.get(s) + "  ");
                }  
            }

2.List<Map<String,Object>> listMap= null;

    for(int i = 0; i<len; i++){
      Map<String,Object> map1 = listMap.get(i);
      for (Object o : map1.keySet()) {
    		System.out.print("key=" + o + " value=" + mapMax.get(o));
    	}
     }

3.List<Map<String,Object>> resultList=new ArrayList<Map<String,Object>>();

    for (Map<String, Object> map : resultList) {
                for (String s : map.keySet()) {
                    System.out.print( map.get(s) );
                } 
           }

4.List<Object[]> list= new ArrayList<Object[]>();

    for (Object[] qwe : list) {
    			System.out.print("list[0]"+qwe[0]);
    			System.out.print("list[1]"+qwe[1]);
    		}

5.遍历一维数组 Int[] arr = {1,2,3,4,5};

    ①．for循环遍历
    for(int i=0;i<arr.length;i++){
         System.out.println( arr[i] ); 
      }
    ②．将数组转换为字符串输出
    System.out.println( Arrays.toString(arr) );
    ③．使用foreach循环遍历数组
    for( int a : arr ){
          System.out.println( a + “” );  
     }

6.遍历二维数组

    public static void main(String args[]) {
    		int arr[][] = { { 1 }, { 2, 3 }, { 4, 5, 6 }, { 7, 8, 9, 10 } };
    ①．方法一
    		for (int x = 0; x < arr.length; x++) {
    			for (int y = 0; y < arr[x].length; y++) {
    				System.out.print(arr[x][y] + "，");
    			}
    			System.out.println("");
    		}
    ②．方法二
            //遍历二维数组中每一个一维数组
             for(int[] cells : arr) {
                //遍历一维数组中每一个元素
                 for(int cell : cells) {
                    System.out.print(cell+" ");
                 } 
                  System.out.println();
             }
    	}

7.遍历Map对象 Map<Integer, Integer> map = new HashMap<Integer, Integer>();

     //遍历map中的键 
	    for (Integer key : map.keySet()) { 
	         System.out.println("Key = " + key); 
	     } 
    //遍历map中的值 
	    for (Integer value : map.values()) { 
	      System.out.println("Value = " + value); 
	    }
    //键值都需要时使用
	    for (Map.Entry<Integer, Integer> entry : map.entrySet()) { 
	      System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue()); 
	    }

8.HashMap的遍历
1.使用迭代器

	    Map map = new HashMap();
	    　　Iterator iter = map.entrySet().iterator();
	    　　while (iter.hasNext()) {
	    　　Map.Entry entry = (Map.Entry) iter.next();
	    　　Object key = entry.getKey();
	    　　Object val = entry.getValue();
	    }

2.for each遍历

     Map<String, String> map = new HashMap<String, String>();
	    ①．for (String key : map.keySet()) {
	    	    map.get(key);
	    }
	    ②．for (Entry<String, String> entry : map.entrySet()) {
	    	entry.getKey();
	    	entry.getValue();
	    }

9.Set集合的遍历
①.迭代遍历：

   Set<String> set = new HashSet<String>();  
	    Iterator<String> a= set.iterator();  
	    while (a.hasNext()) {  
	      String str = a.next();  
	      System.out.println(str);  
	    }   

②.for循环遍历：

 for (String str : set) {  
	          System.out.println(str);  
	    }  

③.set为object类型

    Set<Object> set = new HashSet<Object>();
	    	for(Object obj: set) {
	    		if (obj instanceof Character) {
	    			char chr = (Character)obj;
	    			System.out.println("for: "+chr);
	    		}
	    }