StringUtils.java

/*
 * Copyright 2014 Red Hat, Inc. and/or its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.dashbuilder.common.client;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

public class StringUtils {

    /**
     * <p>Checks if a String is empty ("") or null.</p>
     *
     * <pre>
     * StringUtils.isEmpty(null)      = true
     * StringUtils.isEmpty("")        = true
     * StringUtils.isEmpty(" ")       = false
     * StringUtils.isEmpty("bob")     = false
     * StringUtils.isEmpty("  bob  ") = false
     * </pre>
     *
     * <p>NOTE: This method changed in Lang version 2.0.
     * It no longer trims the String.
     * That functionality is available in isBlank().</p>
     *
     * @param str  the String to check, may be null
     * @return <code>true</code> if the String is empty or null
     */
    public static boolean isEmpty(String str) {
        return str == null || str.length() == 0;
    }

    /**
     * <p>Checks if a String is whitespace, empty ("") or null.</p>
     *
     * <pre>
     * StringUtils.isBlank(null)      = true
     * StringUtils.isBlank("")        = true
     * StringUtils.isBlank(" ")       = true
     * StringUtils.isBlank("bob")     = false
     * StringUtils.isBlank("  bob  ") = false
     * </pre>
     *
     * @param str  the String to check, may be null
     * @return <code>true</code> if the String is null, empty or whitespace
     */
    public static boolean isBlank(String str) {
        int strLen;
        if (str == null || (strLen = str.length()) == 0) {
            return true;
        }
        for (int i = 0; i < strLen; i++) {
            if (!Character.isSpace(str.charAt(i))) {
                return false;
            }
        }
        return true;
    }

    /**
     * <p>Joins the elements of the provided array into a single String
     * containing the provided list of elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * A <code>null</code> separator is the same as an empty String ("").
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.join(null, *)                = null
     * StringUtils.join([], *)                  = ""
     * StringUtils.join([null], *)              = ""
     * StringUtils.join(["a", "b", "c"], "--")  = "a--b--c"
     * StringUtils.join(["a", "b", "c"], null)  = "abc"
     * StringUtils.join(["a", "b", "c"], "")    = "abc"
     * StringUtils.join([null, "", "a"], ',')   = ",,a"
     * </pre>
     *
     * @param array  the array of values to join together, may be null
     * @param separator  the separator character to use, null treated as ""
     * @return the joined String, <code>null</code> if null array input
     */
    public static String join(Object[] array, String separator) {
        if (array == null) {
            return null;
        }
        StringBuilder builder = new StringBuilder();
        for (int i = 0; i < array.length; i++) {
            Object o = array[i];
            if (i > 0) {
                builder.append(separator);
            }
            builder.append(o);
        }
        return builder.toString();
    }

    /**
     * Joins a collection of string with a given delimiter.
     *
     * @param strings The collection of strings to join.
     * @param delimiter The delimiter to use to join them.
     * @return The string built by joining the string with the delimiter.
     */
    public static String join(Collection strings, String delimiter) {
        StringBuilder builder = new StringBuilder();
        Iterator<String> iter = strings.iterator();
        while (iter.hasNext()) {
            builder.append(iter.next());
            if (!iter.hasNext()) {
                break;
            }
            builder.append(delimiter);
        }
        return builder.toString();
    }

    /**
     * <p>Splits the provided text into an array, separator specified.
     * This is an alternative to using StringTokenizer.</p>
     *
     * <p>The separator is not included in the returned String array.
     * Adjacent separators are treated as one separator.
     * For more control over the split use the StrTokenizer class.</p>
     *
     * <p>A {@code null} input String returns {@code null}.</p>
     *
     * <pre>
     * StringUtils.split(null, *)         = null
     * StringUtils.split("", *)           = []
     * StringUtils.split("a.b.c", '.')    = ["a", "b", "c"]
     * StringUtils.split("a..b.c", '.')   = ["a", "b", "c"]
     * StringUtils.split("a:b:c", '.')    = ["a:b:c"]
     * StringUtils.split("a b c", ' ')    = ["a", "b", "c"]
     * </pre>
     *
     * @param str  the String to parse, may be null
     * @param separatorChar  the character used as the delimiter
     * @return an list of parsed Strings, {@code null} if null String input
     */
    public static List<String> split(String str, char separatorChar) {
        List<String> list = new ArrayList<String>();
        if (str == null || str.length() == 0) {
            return list;
        }
        if (str.indexOf(separatorChar) == -1) {
            list.add(str);
            return list;
        }
        int start = 0;
        for (int i = 0; i < str.length(); i++) {
            if (str.charAt(i) == separatorChar) {
                String token = str.substring(start, i).trim();
                if (token.length() > 0) {
                    list.add(token);
                }
                start = i+1;
            }
        }
        String token = str.substring(start, str.length()).trim();
        if (token.length() > 0) {
            list.add(token);
        }
        return list;
    }
}