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A set of utilities and tools to speed up and ease programming in Java.
There is a newer version: 0.5
/*
 * (c) 2005 David B. Bracewell
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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 com.davidbracewell.string;

import com.davidbracewell.function.SerializableFunction;
import com.google.common.base.CharMatcher;
import com.google.common.base.Preconditions;

import java.text.Normalizer;
import java.util.regex.Pattern;

/**
 * @author David B. Bracewell
 */
public enum StringFunctions implements SerializableFunction {
  /**
   * Transforms a string into upper case format
   */
  UPPER_CASE {
    @Override
    public String apply(String input) {
      return input == null ? null : input.toUpperCase();
    }
  },
  /**
   * Transforms a string into lower case format
   */
  LOWER_CASE {
    @Override
    public String apply(String input) {
      return input == null ? null : input.toLowerCase();
    }
  },
  /**
   * Transforms a string into title case format
   */
  TITLE_CASE {
    @Override
    public String apply(String input) {
      if (input == null) {
        return null;
      }
      if (input.isEmpty()) {
        return input;
      }
      char[] chars = input.toLowerCase().toCharArray();
      chars[0] = Character.toUpperCase(chars[0]);
      for (int i = 1; i < input.length() - 1; i++) {
        if (Character.isWhitespace(chars[i - 1])) {
          chars[i] = Character.toUpperCase(chars[i]);
        }
      }
      return new String(chars);
    }
  },
  /**
   * Reverses a string
   */
  REVERSE {
    @Override
    public String apply(String input) {
      return input == null ? null : new StringBuilder(input).reverse().toString();
    }
  },
  /**
   * Trims a function using unicode whitespace and invisible characters
   */
  TRIM {
    @Override
    public String apply(String input) {
      return input == null ? null : CharMatcher.INVISIBLE.trimFrom(CharMatcher.WHITESPACE.trimFrom(input));
    }
  },
  /**
   * Normalizes the string using {@link java.text.Normalizer.Form#NFKC}
   */
  CANONICAL_NORMALIZATION {
    @Override
    public String apply(String input) {
      return input == null ? null : Normalizer.normalize(input, Normalizer.Form.NFKC);
    }
  },
  /**
   * Normalizes the string using by removing diacritics
   */
  DIACRITICS_NORMALIZATION {
    @Override
    public String apply(String input) {
      return input == null ? null :
        Normalizer.normalize(
          Normalizer.normalize(input, Normalizer.Form.NFD)
            .replaceAll("\\p{InCombiningDiacriticalMarks}+", ""),
          Normalizer.Form.NFC);
    }
  },
  LEFT_TRIM {
    @Override
    public String apply(String input) {
      if (input == null) {
        return null;
      }
      return CharMatcher.INVISIBLE.and(CharMatcher.BREAKING_WHITESPACE).and(CharMatcher.WHITESPACE).trimLeadingFrom(input);
    }
  },
  RIGHT_TRIM {
    @Override
    public String apply(String input) {
      if (input == null) {
        return null;
      }
      return CharMatcher.INVISIBLE.and(CharMatcher.BREAKING_WHITESPACE).and(CharMatcher.WHITESPACE).trimTrailingFrom(input);
    }
  },
  NULL_TO_EMPTY {
    @Override
    public String apply(String input) {
      return input == null ? StringUtils.EMPTY : input;
    }
  };


  /**
   * Creates a function that performs a regular expression replacement on a
   * string
   *
   * @param pattern     The regex pattern
   * @param replacement The replacement text
   * @return The function
   */
  public static SerializableFunction REGEX_REPLACE(String pattern, String replacement) {
    return REGEX_REPLACE(
      Pattern.compile(Preconditions.checkNotNull(pattern)),
      Preconditions.checkNotNull(replacement));
  }

  /**
   * Creates a function that performs a regular expression replacement on a
   * string
   *
   * @param pattern     The regex pattern
   * @param replacement The replacement text
   * @return The function
   */
  public static SerializableFunction REGEX_REPLACE(final Pattern pattern, final String replacement) {
    Preconditions.checkNotNull(pattern);
    Preconditions.checkNotNull(replacement);
    return arg0 -> arg0 == null ? null : pattern.matcher(arg0).replaceAll(replacement);
  }


}//END OF StringFunctions