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Carrot2 Text Clustering Library
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/*
 * Carrot2 project.
 *
 * Copyright (C) 2002-2020, Dawid Weiss, Stanisław Osiński.
 * All rights reserved.
 *
 * Refer to the full license file "carrot2.LICENSE"
 * in the root folder of the repository checkout or at:
 * https://www.carrot2.org/carrot2.LICENSE
 */
package org.carrot2.util;

/** A number of useful methods for working with char [] arrays. */
public class CharArrayUtils {
  public static final char[] EMPTY_ARRAY = new char[0];

  /** In place to lower case conversion. In input array is returned for convenience. */
  public static char[] toLowerCaseInPlace(char[] array) {
    for (int i = array.length; --i >= 0; ) {
      array[i] = Character.toLowerCase(array[i]);
    }

    return array;
  }

  /** To lower case conversion. A copy of the input array will be created. */
  public static char[] toLowerCaseCopy(char[] array) {
    return toLowerCaseInPlace(array.clone());
  }

  /**
   * Computes and returns the ratio of capitalized letters in the string to the numbers of all
   * letters.
   */
  public static float getCapitalizedRatio(char[] string) {
    final int len = string.length;

    if (len == 0) return 0;

    int capitalized = 0;
    for (int i = len; --i >= 0; ) {
      if (Character.isUpperCase(string[i])) capitalized++;
    }

    return capitalized / (float) len;
  }

  /** Returns true if the input array contains any capitalized characters. */
  public static boolean hasCapitalizedLetters(char[] string) {
    for (int i = string.length; --i >= 0; ) {
      if (Character.isUpperCase(string[i])) return true;
    }

    return false;
  }

  /** Returns a capitalized copy of the input character array. */
  public static char[] toCapitalizedCopy(char[] string) {
    final int len = string.length;

    if (len == 0) return string;

    final char[] lowerCase = toLowerCaseCopy(string);
    lowerCase[0] = Character.toUpperCase(lowerCase[0]);

    return lowerCase;
  }

  /**
   * Convert to lower case (character-by-character) and save the result into buffer.
   *
   * @param word The word to be converted to lower case.
   * @param buffer The buffer where the result should be saved.
   * @return Returns true if at least one character was changed between word
   *      and buffer. false indicates an identical copy.
   * @throws AssertionError If buffer is smaller than word.
   */
  public static boolean toLowerCase(char[] word, char[] buffer) {
    return toLowerCase(word, buffer, 0, word.length);
  }

  /**
   * Convert to lower case (character-by-character) and save the result into buffer.
   * The buffer must have at least length characters.
   *
   * @param word The word to be converted to lower case.
   * @param buffer The buffer where the result should be saved.
   * @param start the index in the word at which to start
   * @param length the number of characters from word to process
   * @return Returns true if at least one character was changed between word
   *      and buffer. false indicates an identical copy.
   * @throws AssertionError If buffer is smaller than length.
   * @throws AssertionError If start + length is smaller than the length word
   *     .
   */
  public static boolean toLowerCase(char[] word, char[] buffer, int start, int length) {
    assert buffer.length >= length : "Buffer too small.";
    assert start + length <= word.length : "Word too short.";
    assert start >= 0 : "Start must be >= 0";

    boolean different = false;
    char in, out;
    for (int i = length; --i >= 0; ) {
      buffer[i] = out = Character.toLowerCase(in = word[i + start]);
      different |= (in != out);
    }
    return different;
  }
}