How to trim a java stringbuilder?

Question

I have a StringBuilder object that needs to be trimmed (i.e. all whitespace chars /u0020 and below removed from either end).

I can\'t seem to find a method in string

Answer 1

I made some code. It works and the test cases are there for you to see. Let me know if this is okay.

Main code -

public static StringBuilder trimStringBuilderSpaces(StringBuilder sb) {

    int len = sb.length();

    if (len > 0) {

            int start = 0;
            int end = 1;
            char space = ' ';
            int i = 0;

            // Remove spaces at start
            for (i = 0; i < len; i++) {
                if (sb.charAt(i) != space) {
                    break;
                }
            }

            end = i;
            //System.out.println("s = " + start + ", e = " + end);
            sb.delete(start, end);

            // Remove the ending spaces
            len = sb.length();

            if (len > 1) {

                for (i = len - 1; i > 0; i--) {
                    if (sb.charAt(i) != space) {
                        i = i + 1;
                        break;
                    }
                }

                start = i;
                end = len;// or len + any positive number !

                //System.out.println("s = " + start + ", e = " + end);
                sb.delete(start, end);

            }

    }

    return sb;
}

The full code with test -

package source;

import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.ArrayList;

public class StringBuilderTrim {

    public static void main(String[] args) {
        testCode();
    }

    public static void testCode() {

        StringBuilder s1 = new StringBuilder("");
        StringBuilder s2 = new StringBuilder(" ");
        StringBuilder s3 = new StringBuilder("  ");
        StringBuilder s4 = new StringBuilder(" 123");
        StringBuilder s5 = new StringBuilder("  123");
        StringBuilder s6 = new StringBuilder("1");
        StringBuilder s7 = new StringBuilder("123 ");
        StringBuilder s8 = new StringBuilder("123  ");
        StringBuilder s9 = new StringBuilder(" 123 ");
        StringBuilder s10 = new StringBuilder("  123  ");

        /*
         * Using a rough form of TDD here. Initially, one one test input
         * "test case" was added and rest were commented. Write no code for the
         * method being tested. So, the test will fail. Write just enough code
         * to make it pass. Then, enable the next test. Repeat !!!
         */
        ArrayList ins = new ArrayList();
        ins.add(s1);
        ins.add(s2);
        ins.add(s3);
        ins.add(s4);
        ins.add(s5);
        ins.add(s6);
        ins.add(s7);
        ins.add(s8);
        ins.add(s9);
        ins.add(s10);

        // Run test
        for (StringBuilder sb : ins) {
            System.out
                    .println("\n\n---------------------------------------------");
            String expected = sb.toString().trim();
            String result = trimStringBuilderSpaces(sb).toString();
            System.out.println("In [" + sb + "]" + ", Expected [" + expected
                    + "]" + ", Out [" + result + "]");
            if (result.equals(expected)) {
                System.out.println("Success!");
            } else {
                System.out.println("FAILED!");
            }
            System.out.println("---------------------------------------------");
        }

    }

    public static StringBuilder trimStringBuilderSpaces(StringBuilder inputSb) {

        StringBuilder sb = new StringBuilder(inputSb);
        int len = sb.length();

        if (len > 0) {

            try {

                int start = 0;
                int end = 1;
                char space = ' ';
                int i = 0;

                // Remove spaces at start
                for (i = 0; i < len; i++) {
                    if (sb.charAt(i) != space) {
                        break;
                    }
                }

                end = i;
                //System.out.println("s = " + start + ", e = " + end);
                sb.delete(start, end);

                // Remove the ending spaces
                len = sb.length();

                if (len > 1) {

                    for (i = len - 1; i > 0; i--) {
                        if (sb.charAt(i) != space) {
                            i = i + 1;
                            break;
                        }
                    }

                    start = i;
                    end = len;// or len + any positive number !

                    //System.out.println("s = " + start + ", e = " + end);
                    sb.delete(start, end);

                }

            } catch (Exception ex) {

                StringWriter sw = new StringWriter();
                PrintWriter pw = new PrintWriter(sw);
                ex.printStackTrace(pw);
                sw.toString(); // stack trace as a string

                sb = new StringBuilder("\nNo Out due to error:\n" + "\n" + sw);
                return sb;
            }

        }

        return sb;
    }
}