如何将 Java 字符串一分为二，其中第一个子字符串不长于 x 并以整个单词结尾

Question

I'm at a loss with dividing a string into 2 substrings. The first substring's length should be no more than 35 and it should end with the end of the word. So, if the 35 limit falls mid-word, then break the string when this word starts (let's say on 32). by word I mean any combo of non-space characters. words are divided by spaces. The second substring can be of any length and, consequently, should start with the start of a word. The string is always bigger than 35 and doesn't have a pattern. How can I implement it? Thanks in advance!

Example:

"Lordem ipsum dolor sit amet, $200 cons(35 chars until here)ectetur adipiscing elit, №22sed 70 % do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat."

This is a long String. Then i need to get to strings : "Lordem ipsum dolor sit amet, $200" (fewer than 35 and ends where word ends) and the rest into one big separate substring

Answer 1

You can use StringTokenizer:

import java.util.Arrays;
import java.util.StringTokenizer;

public class Test {

    public static void main(String[] args){
        String str = "Lordem ipsum dolor sit amet, $200 cons(35 chars until here)ectetur adipiscing elit, №22sed 70 % do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.";
        StringTokenizer strToken  = new StringTokenizer(str," ",true);
        String first  = "";
        String second = "";

        while(strToken.hasMoreTokens()){
            String next = strToken.nextToken();
            if((first+next).length() < 35){
                first += next;
            }
            else{
                break;
            }
            second = str.substring(first.length());
        }
        System.out.println(first);
        System.out.println(second);
    }
}

Or if you are on java 9 or higher and want to try streams :

import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.Collectors;

public class Test {

    public static void main(String[] args){
        String str = "Lordem ipsum dolor sit amet, $200 cons(35 chars until here)ectetur adipiscing elit, №22sed 70 % do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.";

        //split at space and keep delimiters
        String[] splited = str.split("((?<= )|(?= ))");

        AtomicInteger ai = new AtomicInteger(0);
        String f = Arrays.stream(splited).takeWhile(i -> ai.addAndGet(i.length()) < 35).collect(Collectors.joining());

        AtomicInteger bi = new AtomicInteger(0);
        String s = Arrays.stream(splited).dropWhile(i -> bi.addAndGet(i.length()) < 35).collect(Collectors.joining());

        System.out.println(f);
        System.out.println(s);
    }
}

Answer 2

You can use the following approach with an input of 35 to get the desired result.

public static String[] splitAtLengthOrBeforeWord(String s, int length) {
    if(length < 0) {
        throw new IllegalArgumentException("length must be greater than 0");
    }

    if(s.length() < length) {
        return new String[] { s, "" };
    }
    
    for(int i = length - 1; i >= 0; i--) {
        int c = s.charAt(i);
        if(Character.isWhitespace(c)) {
            return new String[] { s.substring(0, i), s.substring(i) };
        }
    }
    return new String[] { "", s };
}

Answer 3

You can use lastindexOf method from string class, first check if character at 35 index is space just simple split else you can split on 35 and get last index of space that index will give you start of word and that is what we trying to figure out. Below is code working on this logic. You can add other safety checks as required.

    public static void main(String[] args) {
    String str = "Lordem ipsum dolor sit amet, $200 cons(35 chars until here)ectetur adipiscing elit, №22sed 70 % do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.";
    String str1, str2 = "";
    if (str.charAt(35) == ' ') {
        str1 = str.substring(0, 35);
        str2 = str.substring(36, str.length());
    }
    else {
        String temp = str.substring(0, 35);
        int ind = temp.lastIndexOf(' ');
        str1 = str.substring(0, ind);
        str2 = str.substring(ind + 1, str.length());
    }
    System.out.println(str1);
    System.out.println(str2);
   }

}