如何使用Java中的方法从巨大的字符串中删除相同的字符

Question

I have a string of 10^1000 characters.where we cant run a loop to check one by one..then what should i do?

i do like

public class test {

public static void main(String[] args) {

    String input = new String("abbc");
    String output = new String();

    for (int i = 0; i < input.length(); i++) {
        for (int j = 0; j < output.length(); j++) {
            if (input.charAt(i) != output.charAt(j)) {
                output = output + input.charAt(i);
            }
        }
    }

    System.out.println(output);

}
}

I do it in this way to remove the all duplicate character from a string .but it is not efficient when the input.length() is too large.

Answer 1

You can try to convert the string to an array of char, and store it in a LinkedHashSet. That will preserve your ordering, and remove duplicates

char[] chars = string.toCharArray();
Set<Character> charSet = new LinkedHashSet<Character>();
for (char c : chars) {
    charSet.add(c);
}

StringBuilder sb = new StringBuilder();
for (Character character : charSet) {
    sb.append(character);
}
System.out.println(sb.toString());

Answer 2

If your String has separator I think that you could use a Set.

Set<String> set = new HashSet<String>(Arrays.asList(text.split(" ")));

Or in java 8:

Set<String> set = Arrays.stream(text.split(" ")).collect(Collectors.toSet());

Answer 3

You could maintain a set of characters ( Set<Character> ) you already did encounter for 0 .. (i-1).

As this reeks of homework I leave it to that.