示例
@Test
void str2arr() {
String ids = "1,2,3,4,5,6";
//字符串 --> String数组
String[] arrayStr = ids.split(",");
System.out.println(arrayStr);
}
@Test
void list2Str() {
List<String> list = new ArrayList<>();
for (int i = 0; i < 4; i++) {
list.add("_" + i);
}
//List<String> --> ,分隔的String
String Str2 = String.join(",", list);
}
@Test
void arr2List() {
int[] arr = {1,2,3};
List<int[]> ints = Arrays.asList(arr);
System.out.println(ints);
Integer[] arr2 = {1,2,3};
List<Integer> ints2 = Arrays.asList(arr2);
System.out.println(ints2);
// Arrays.asList()返回一个受指定数组支持的固定大小的列表。所以不能做Add、Remove等操作
// ints2.add(4);
// System.out.println(ints2);
List<Integer> ints3 = new ArrayList<>(ints2);
ints3.add(4);
System.out.println(ints3);
}
@Test
void arr2List2() {
String[] arrayStr = {"1", "2", "3"};
//String数组 --> List<String>
List<String> listStr = Arrays.stream(arrayStr).collect(Collectors.toList());
int[] arrayInt = {1, 2, 3};
//int数组 --> List<Integer>
List<Integer> listInt = Arrays.stream(arrayInt).boxed().collect(Collectors.toList());
}
@Test
void arr2Set() {
Integer[] arr2 = {1,2,3};
Set<Integer> set = new HashSet<>(Arrays.asList(arr2));
System.out.println(set);
}
@Test
void List2Arr() {
List<String> list = new ArrayList<>();
for (int i = 0; i < 4; i++) {
list.add("1-"+i);
}
String[] arr = new String[list.size()];
list.toArray(arr);
}
@Test
void List2Set() {
List<String> list = new ArrayList<>();
for (int i = 0; i < 4; i++) {
list.add("1-"+i);
}
Set<String> set = new HashSet<>(list);
System.out.println(set);
}
@Test
void Set2List() {
Set<String> set = new HashSet<>();
for (int i = 0; i < 4; i++) {
set.add("1-"+i);
}
List<String> list = new ArrayList<>(set);
System.out.println(list);
}
@Test
void arr2arr() {
String ids = "1,2,3,4,5,6";
//字符串 --> String数组
String[] arrayStr = ids.split(",");
//String数组 --> int数组
int[] arrayInt = Arrays.stream(arrayStr).mapToInt(Integer::parseInt).toArray();
// int数组 --> String数组
String[] arrayStr2 = Arrays.stream(arrayInt).mapToObj(String::valueOf).toArray(String[]::new);
}
@Test
void testStream() {
List<String> stringList = new ArrayList<>();
stringList.add("zhang3");
stringList.add("lis4");
stringList.add("wang5");
stringList.add("zhao6");
List<Map<String, String>> stringList1 = stringList.stream().map(item ->
{
Map<String, String> map = new HashMap<>();
map.put("name", item.toUpperCase());
map.put("class", "1");
return map;
}
).collect(Collectors.toList());
System.out.println(stringList1);
}