Java 集合将字符串转换为字符列表 [英] Java collections convert a string to a list of characters

问题描述

我想将包含 abc 的字符串转换为字符列表和字符哈希集.我怎样才能在 Java 中做到这一点?

I would like to convert the string containing abc to a list of characters and a hashset of characters. How can I do that in Java ?

List<Character> charList = new ArrayList<Character>("abc".toCharArray());

推荐答案

你必须要么使用循环，要么创建一个像 Arrays.asList 这样处理原始字符数组(或直接在字符串上).

You will have to either use a loop, or create a collection wrapper like Arrays.asList which works on primitive char arrays (or directly on strings).

List<Character> list = new ArrayList<Character>();
Set<Character> unique = new HashSet<Character>();
for(char c : "abc".toCharArray()) {
    list.add(c);
    unique.add(c);
}

这是一个 Arrays.asList 类似字符串的包装器:

Here is an Arrays.asList like wrapper for strings:

public List<Character> asList(final String string) {
    return new AbstractList<Character>() {
       public int size() { return string.length(); }
       public Character get(int index) { return string.charAt(index); }
    };
}

不过，这是一个不可变的列表.如果您想要一个可变列表，请将其与 char[] 一起使用:

This one is an immutable list, though. If you want a mutable list, use this with a char[]:

public List<Character> asList(final char[] string) {
    return new AbstractList<Character>() {
       public int size() { return string.length; }
       public Character get(int index) { return string[index]; }
       public Character set(int index, Character newVal) {
          char old = string[index];
          string[index] = newVal;
          return old;
       }
    };
}

与此类似，您可以为其他原始类型实现此功能.请注意，通常不建议使用它，因为对于每次访问您会进行装箱和拆箱操作.

Analogous to this you can implement this for the other primitive types. Note that using this normally is not recommended, since for every access you would do a boxing and unboxing operation.

Guava 库 包含 几个原始数组类的类似列表包装方法，例如Chars.asList，和Lists.charactersOf(String).

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