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Java library for generating Swiss QR bills

There is a newer version: 3.3.1

//
// Swiss QR Bill Generator
// Copyright (c) 2018 Manuel Bleichenbacher
// Licensed under MIT License
// https://opensource.org/licenses/MIT
//

package net.codecrete.qrbill.generator;

/**
 * Helper function for processing strings.
 */
public class Strings {

    private Strings() {
        // Do not create instances
    }

    /**
     * Returns string with leading and trailing whitespace removed
     * 
     * For empty strings or {@code null}, {@code null} is returned.
     * 
     *
     * @param value string to trim or {@code null}
     * @return trimmed string
     */
    public static String trimmed(String value) {
        if (value == null)
            return null;
        value = value.trim();
        if (value.length() == 0)
            return null;
        return value;
    }

    /**
     * Returns string without white space
     *
     * @param value string to process (non null)
     * @return resulting string with all whitespace removed
     */
    public static String whiteSpaceRemoved(String value) {
        StringBuilder sb = null;
        int len = value.length();
        int lastCopied = 0;
        for (int i = 0; i < len; i++) {
            char ch = value.charAt(i);
            if (ch <= ' ') {
                if (i > lastCopied) {
                    if (sb == null)
                        sb = new StringBuilder();
                    sb.append(value, lastCopied, i);
                }
                lastCopied = i + 1;
            }
        }

        if (sb == null) {
            if (lastCopied == 0)
                return value;

            if (lastCopied == len)
                return "";

            return value.substring(lastCopied, len);
        }

        if (lastCopied < len)
            sb.append(value, lastCopied, len);

        return sb.toString();
    }

    /**
     * Tests if a string is null or empty
     * 
     * A string consisting of all whitespace is considered empty.
     * 
     *
     * @param value string to test
     * @return boolean indicating if string is null or empty
     */
    public static boolean isNullOrEmpty(String value) {
        return value == null || value.trim().length() == 0;
    }
}