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/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you 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.elasticsearch.hadoop.yarn.util;

import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.StringTokenizer;


/**
 * Utility class around Strings. Used to remove dependency on other libraries that might (or not) be available at runtime.
 */
public abstract class StringUtils {

    public static final Charset UTF_8 = Charset.forName("UTF-8");
    public static final String EMPTY = "";

    public static boolean hasLength(CharSequence sequence) {
        return (sequence != null && sequence.length() > 0);
    }

    public static boolean hasText(CharSequence sequence) {
        if (!hasLength(sequence)) {
            return false;
        }
        int length = sequence.length();
        for (int i = 0; i < length; i++) {
            if (!Character.isWhitespace(sequence.charAt(i))) {
                return true;
            }
        }
        return false;
    }

    public static List tokenize(String string) {
        return tokenize(string, ",");
    }

    public static List tokenize(String string, String delimiters) {
        return tokenize(string, delimiters, true, true);
    }

    public static List tokenize(String string, String delimiters, boolean trimTokens, boolean ignoreEmptyTokens) {
        if (string == null) {
            return Collections.emptyList();
        }
        StringTokenizer st = new StringTokenizer(string, delimiters);
        List tokens = new ArrayList();
        while (st.hasMoreTokens()) {
            String token = st.nextToken();
            if (trimTokens) {
                token = token.trim();
            }
            if (!ignoreEmptyTokens || token.length() > 0) {
                tokens.add(token);
            }
        }
        return tokens;
    }

    public static String concatenate(Collection list, String delimiter) {
        if (list == null || list.isEmpty()) {
            return EMPTY;
        }
        if (delimiter == null) {
            delimiter = EMPTY;
        }
        StringBuilder sb = new StringBuilder();

        for (Object object : list) {
            sb.append(object.toString());
            sb.append(delimiter);
        }

        sb.setLength(sb.length() - delimiter.length());
        return sb.toString();
    }

    public static String concatenate(Object[] array, String delimiter) {
        if (array == null || array.length == 0) {
            return EMPTY;
        }
        if (delimiter == null) {
            delimiter = EMPTY;
        }

        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < array.length; i++) {
            if (i > 0) {
                sb.append(delimiter);
            }
            sb.append(array[i]);
        }
        return sb.toString();
    }

    public static String deleteWhitespace(CharSequence sequence) {
        if (!hasLength(sequence)) {
            return EMPTY;
        }

        StringBuilder sb = new StringBuilder(sequence.length());
        for (int i = 0; i < sequence.length(); i++) {
            char currentChar = sequence.charAt(i);
            if (!Character.isWhitespace(currentChar)) {
                sb.append(currentChar);
            }
        }
        // return the initial String if no whitespace is found
        return (sb.length() == sequence.length() ? sequence.toString() : sb.toString());
    }

    public static boolean isLowerCase(CharSequence string) {
        for (int index = 0; index < string.length(); index++) {
            if (Character.isUpperCase(string.charAt(index))) {
                return false;
            }
        }
        return true;
    }
}