Java 集合将字符串转换为字符列表

The most straightforward way is to use a for loop to add elements to a new List:

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


for (char c : abc.toCharArray()) {
charList.add(c);
}

Similarly, for a Set:

String abc = "abc";
Set<Character> charSet = new HashSet<Character>();


for (char c : abc.toCharArray()) {
charSet.add(c);
}

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);
}

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); }
};
}

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;
}
};
}

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.

The Guava library contains similar List wrapper methods for several primitive array classes, like Chars.asList, and a wrapper for String in Lists.charactersOf(String).

Create an empty list of Character and then make a loop to get every character from the array and put them in the list one by one.

List<Character> characterList = new ArrayList<Character>();
char arrayChar[] = abc.toCharArray();
for (char aChar : arrayChar)
{
characterList.add(aChar); //  autoboxing
}

The lack of a good way to convert between a primitive array and a collection of its corresponding wrapper type is solved by some third party libraries. Guava, a very common one, has a convenience method to do the conversion:

List<Character> characterList = Chars.asList("abc".toCharArray());
Set<Character> characterSet = new HashSet<Character>(characterList);

In Java8 you can use streams I suppose. List of Character objects:

List<Character> chars = str.chars()
.mapToObj(e->(char)e).collect(Collectors.toList());

And set could be obtained in a similar way:

Set<Character> charsSet = str.chars()
.mapToObj(e->(char)e).collect(Collectors.toSet());

Use a Java 8 Stream.

myString.chars().mapToObj(i -> (char) i).collect(Collectors.toList());

Breakdown:

myString
.chars() // Convert to an IntStream
.mapToObj(i -> (char) i) // Convert int to char, which gets boxed to Character
.collect(Collectors.toList()); // Collect in a List<Character>

(I have absolutely no idea why String#chars() returns an IntStream.)

You can do this without boxing if you use Eclipse Collections:

CharAdapter abc = Strings.asChars("abc");
CharList list = abc.toList();
CharSet set = abc.toSet();
CharBag bag = abc.toBag();

Because CharAdapter is an ImmutableCharList, calling collect on it will return an ImmutableList.

ImmutableList<Character> immutableList = abc.collect(Character::valueOf);

If you want to return a boxed List, Set or Bag of Character, the following will work:

LazyIterable<Character> lazyIterable = abc.asLazy().collect(Character::valueOf);
List<Character> list = lazyIterable.toList();
Set<Character> set = lazyIterable.toSet();
Bag<Character> set = lazyIterable.toBag();

Note: I am a committer for Eclipse Collections.

IntStream can be used to access each character and add them to the list.

String str = "abc";
List<Character> charList = new ArrayList<>();
IntStream.range(0,str.length()).forEach(i -> charList.add(str.charAt(i)));

Using Java 8 - Stream Funtion:

Converting A String into Character List:

ArrayList<Character> characterList =  givenStringVariable
.chars()
.mapToObj(c-> (char)c)
.collect(collectors.toList());

Converting A Character List into String:

 String givenStringVariable =  characterList
.stream()
.map(String::valueOf)
.collect(Collectors.joining())

List<String> result = Arrays.asList("abc".split(""));

To get a list of Characters / Strings -

List<String> stringsOfCharacters = string.chars().
mapToObj(i -> (char)i).
map(c -> c.toString()).
collect(Collectors.toList());