问题

获取以下列表中的元素方法：

List<String> list = new ArrayList<>();

List<String> getRoles = 
buildRolesList(list, role).stream()
    .map(String::trim)
    .map(String::toLowerCase)
    .map(str->str.replace("[",""))
    .map(str->str.replace("]",""))
    .collect(Collectors.toCollection(ArrayList::new));

getRoles = "admin, user" ---这是我得到的列表，但想要的列表是["admin","user"]分割的

如何将列表的值设置为[0->"admin",1->"user"]

上述结果的大小为1，但想要的大小是2。

List<String> list = new ArrayList<>();

List<String> getRoles = 
buildRolesList(list, role).stream()
    .map(String::trim)
    .map(String::toLowerCase)
    .map(str->str.replace ( "[","" ))
    .map(str->str.replace ( "]","" ))
    .collect( Collectors.toCollection ( ArrayList::new ) );

答案1

得分: 1

假设你有一个类似于 `"[admin, user]"` 的字符串列表。然后你做得差不多了，只是忘记将字符串拆分为单独的角色。

```java
public static void main(String... args) {
    List<String> list = List.of("[admin, user]",
                                "[owner, developer]");

    Set<String> roles = getRoles(list);
    System.out.println(roles);  // [owner, admin, developer, user]
}

public static Set<String> getRoles(List<String> list) {
    return list.stream()
               .map(String::toLowerCase)
               .map(Foo::getRoles)
               .flatMap(Set::stream)
               .collect(Collectors.toSet());
}

private static Set<String> getRoles(String str) {
    return Stream.of(str)
                 .map(s -> s.replace("[", ""))
                 .map(s -> s.replace("]", ""))
                 .map(s -> s.split("\\s*,\\s*"))
                 .flatMap(Arrays::stream)
                 .collect(Collectors.toSet());
}

public static void main(String... args) {
    List<String> list = List.of("[admin, user]",
                                "[owner, developer]");

    Set<String> roles = getRoles(list);
    System.out.println(roles);  // [owner, admin, developer, user]
}

public static Set<String> getRoles(List<String> list) {
    return list.stream()
               .map(String::toLowerCase)
               .map(Foo::getRoles)
               .flatMap(Set::stream)
               .collect(Collectors.toSet());
}

private static Set<String> getRoles(String str) {
    return Stream.of(str)
                 .map(s -> s.replace("[", ""))
                 .map(s -> s.replace("]", ""))
                 .map(s -> s.split("\\s*,\\s*"))
                 .flatMap(Arrays::stream)
                 .collect(Collectors.toSet());
}

答案2

得分: 0

将一个列表值拆分为元素的方法
看起来你有一对角色的列表，并且想把它们拆分成大小为2的独立列表。`List.toString()` 所以你能否返回一个所有角色的 `List<String>`，然后将它们分成一对。以下是如何做到的。

List<List> roles = List.of("admin", "user", "steno", "typist"));

List<List> roleLists = new ArrayList<>();

if (roles.size() % 2 != 0) {
System.out.println("Roles must be in pairs");
} else {
for (int i = 0; i < roles.size(); i += 2) {
roleLists.add(new ArrayList<>(List.of(roles.get(i), roles.get(i + 1))));
}
}

然后，当你得到列表的列表时，你可以按以下方式检索值：

for (List lst : roles) {
System.out.println("List -> " + lst);
for (int i = 0; i < lst.size(); i++) {
System.out.printf(" %d -> %s%n", i, lst.get(i));
}
}

输出

List -> [admin, user]
0 -> admin
1 -> user
List -> [steno, typist]
0 -> steno
1 -> typist

否则，只需执行以下操作：

String s = "[admin, user]";

String[] result = s.replaceAll("[\[\]\s+]+","").split(",");
for (int i = 0; i < result.length; i++) {
System.out.printf("%d -> %s%n", i, result[i]);
}

输出

0 -> admin
1 -> user

<details>
<summary>英文:</summary>
&gt;how to split one list value to elements
It looks like you have a list of roles in pairs and want to break that up into separate lists of size 2. `List.toString()` So can&#39;t you instead return a `List&lt;String&gt;` of all the roles and just copy in pairs.  Here is how it would work.

List<List<String>> roles = List.of("admin", "user",
"steno","typist"));

List<List<String>> roleLists = new ArrayList<>();

if (roles.size()%2 != 0) {
System.out.println("Roles must be in pairs");
} else {
for (int i = 0; i < roles.size(); i+=2) {
roleLists.add(new ArrayList<>(List.of(roles.get(i),roles.get(i+1))));
}
}

Then when you get the list of lists you can retrieve the values as follows:

for(List<String> lst : roles) {
System.out.println("List -> " + lst);
for(int i = 0; i < lst.size(); i++) {
System.out.printf(" %d -> %s%n", i, lst.get(i));
}
}

prints

List -> [admin, user]
0 -> admin
1 -> user
List -> [steno, typist]
0 -> steno
1 -> typist

Otherwise, just do the following:

String s = "[admin, user]";

String[] result = s.replaceAll("[\[\]\s+]+","").split(",");
for (int i = 0; i < result.length; i++) {
System.out.printf("%d -> %s%n", i, result[i]);
}

prints

0 -> admin
1 -> user