<转>list,set,地图,数组间的相互转换

<转>list,set,map,数组间的相互转换

原链：http://teamojiao.iteye.com/blog/436139

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1.list转set

Java代码?

1. Set?set?=?new?HashSet(new?ArrayList());????

Java代码??

1. Set?set?=?new?HashSet(new?ArrayList());????

2.set转list

Java代码?

1. List?list?=?new?ArrayList(new?HashSet());????

Java代码??

1. List?list?=?new?ArrayList(new?HashSet());????

3.数组转为list

Java代码?

1. List?stooges?=?Arrays.asList("Larry",?"Moe",?"Curly");????

Java代码??

1. List?stooges?=?Arrays.asList("Larry",?"Moe",?"Curly");????

此时stooges中有有三个元素。?
4.数组转为set?
int[] a = { 1, 2, 3 };??

Java代码?

1. Set?set?=?new?HashSet(Arrays.asList(a));????

Java代码??

1. Set?set?=?new?HashSet(Arrays.asList(a));????

5.map的相关操作。

Java代码?

1. Map?map?=?new?HashMap();??? ??
2. map.put("1",?"a");??? ??
3. map.put('2',?'b');??? ??
4. map.put('3',?'c');??? ??
5. System.out.println(map);??? ??
6. //?输出所有的值??????
7. System.out.println(map.keySet());??? ??
8. //?输出所有的键??????
9. System.out.println(map.values());??? ??
10. //?将map的值转化为List??????
11. List?list?=?new?ArrayList(map.values());??? ??
12. System.out.println(list);??? ??
13. //?将map的值转化为Set??????
14. Set?set?=?new?HashSet(map.values());??? ??
15. System.out.println(set);????

Java代码??

1. Map?map?=?new?HashMap();?????
2. map.put("1",?"a");?????
3. map.put('2',?'b');?????
4. map.put('3',?'c');?????
5. System.out.println(map);?????
6. //?输出所有的值?????
7. System.out.println(map.keySet());?????
8. //?输出所有的键?????
9. System.out.println(map.values());?????
10. //?将map的值转化为List?????
11. List?list?=?new?ArrayList(map.values());?????
12. System.out.println(list);?????
13. //?将map的值转化为Set?????
14. Set?set?=?new?HashSet(map.values());?????
15. System.out.println(set);????

6.list转数组

Java代码?

1. List?list?=?Arrays.asList("a","b");??? ??
2. System.out.println(list);??? ??
3. ??????????? ??
4. String[]?arr?=?(String[])list.toArray(new?String[list.size()]);??? ??
5. System.out.println(Arrays.toString(arr));????

Java代码??

1. List?list?=?Arrays.asList("a","b");?????
2. System.out.println(list);?????
3. ?????????????
4. String[]?arr?=?(String[])list.toArray(new?String[list.size()]);?????
5. System.out.println(Arrays.toString(arr));????

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