1.list转set
- Set set = new HashSet(new ArrayList());
2.set转list
- List list = new ArrayList(new HashSet());
3.数组转为list
- List stooges = Arrays.asList("Larry", "Moe", "Curly");
此时stooges中有有三个元素。注意：此时的list不能进行add操作，否则会报“java.lang.UnsupportedOperationException”，Arrays.asList()返回的是List,而且是一个定长的List，所以不能转换为ArrayList，只能转换为AbstractList
原因在于asList()方法返回的是某个数组的列表形式,返回的列表只是数组的另一个视图,而数组本身并没有消失,对列表的任何操作最终都反映在数组上. 所以不支持remove,add方法的
- String[] arr = {"1", "2"};
- List list = Arrays.asList(arr);
- String[] arr = {"1", "2"};
- List list = Arrays.asList(arr);
4.数组转为set
- int[] a = { 1, 2, 3 };
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- Set set = new HashSet(Arrays.asList(a));
- Set set = new HashSet(Arrays.asList(a));
5.map的相关操作。
- Map map = new HashMap();
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- map.put("1", "a");
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- map.put(‘2‘, ‘b‘);
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- map.put(‘3‘, ‘c‘);
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- System.out.println(map);
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- System.out.println(map.keySet());
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- System.out.println(map.values());
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- List list = new ArrayList(map.values());
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- System.out.println(list);
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- Set set = new HashSet(map.values());
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- System.out.println(set);
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- Map map = new HashMap();
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- map.put("1", "a");
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- map.put(‘2‘, ‘b‘);
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- map.put(‘3‘, ‘c‘);
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- System.out.println(map);
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- System.out.println(map.keySet());
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- System.out.println(map.values());
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- List list = new ArrayList(map.values());
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- System.out.println(list);
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- Set set = new HashSet(map.values());
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- System.out.println(set);
6.list转数组
- List list = Arrays.asList("a","b");
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- System.out.println(list);
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- String[] arr = (String[])list.toArray(new String[list.size()]);
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- System.out.println(Arrays.toString(arr));
java list map set array 转换
原文：http://www.cnblogs.com/xxsl/p/7224070.html
