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Advanced yet easy-to-use escape/unescape library for Java
There is a newer version: 1.1.6.RELEASE
/*
 * =============================================================================
 * 
 *   Copyright (c) 2014, The UNBESCAPE team (http://www.unbescape.org)
 * 
 *   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.unbescape.java;

/**
 * 
 *   Levels defined for Java escape/unescape operations:
 * 
 *
 * 
 *     Level 1: Escape only the basic escape set. Note the result of a level-1 escape
 *         operation might still contain non-ASCII characters if they existed in input, and therefore you
 *         will still need to correctly manage your input/output character encoding settings. Such
 *         basic set consists of:
 *         
 *           The Single Escape Characters:
 *               \b (U+0008),
 *               \t (U+0009),
 *               \n (U+000A),
 *               \f (U+000C),
 *               \r (U+000D),
 *               \" (U+0022),
 *               \' (U+0027),
 *               \\ (U+005C). Note \' is not really needed in
 *               String literals (only in Character literals), so it won't be used until escape level 3.
 *           
 *           
 *               Two ranges of non-displayable, control characters (some of which are already part of the
 *               single escape characters list): U+0000 to U+001F
 *               and U+007F to U+009F.
 *           
 *         
 *     
 *     Level 2: Escape the basic escape set (as defined in level 1), plus all
 *         non-ASCII characters. The result of a level-2 escape operation is therefore always ASCII-only text, and
 *         safer to use in complex scenarios with mixed input/output character encodings.
 *     Level 3: Escape all non-alphanumeric characters, this is, all but those in the
 *         A-Z, a-z and 0-9 ranges. This level
 *         can be safely used for completely escaping texts, including whitespace, line feeds, punctuation, etc. in
 *         scenarios where this adds an extra level of safety.
 *     Level 4: Escape all characters, even alphanumeric ones.
 * 
 *
 * 
 *   For further information, see the Glossary and the References sections at the
 *   documentation for the {@link org.unbescape.java.JavaEscape} class.
 * 
 *
 * @author Daniel Fernández
 *
 * @since 1.0.0
 *
 */
public enum JavaEscapeLevel {

    /**
     * Level 1 escape: escape only the basic escape set: Single Escape Chars plus non-displayable control chars.
     */
    LEVEL_1_BASIC_ESCAPE_SET(1),

    /**
     * Level 2 escape: escape the basic escape set plus all non-ASCII characters (result will always be ASCII).
     */
    LEVEL_2_ALL_NON_ASCII_PLUS_BASIC_ESCAPE_SET(2),

    /**
     * Level 3 escape: escape all non-alphanumeric characteres (escape all but those in the
     * A-Z, a-z and 0-9 ranges).
     */
    LEVEL_3_ALL_NON_ALPHANUMERIC(3),

    /**
     * Level 4 escape: escape all characters, including alphanumeric.
     */
    LEVEL_4_ALL_CHARACTERS(4);




    private final int escapeLevel;


    /**
     * 
     *   Utility method for obtaining an enum value from its corresponding int level value.
     * 
     *
     * @param level the level
     * @return the escape level enum constant, or IllegalArgumentException if level does not exist.
     */
    public static JavaEscapeLevel forLevel(final int level) {
        switch (level) {
            case 1: return LEVEL_1_BASIC_ESCAPE_SET;
            case 2: return LEVEL_2_ALL_NON_ASCII_PLUS_BASIC_ESCAPE_SET;
            case 3: return LEVEL_3_ALL_NON_ALPHANUMERIC;
            case 4: return LEVEL_4_ALL_CHARACTERS;
            default:
                throw new IllegalArgumentException("No escape level enum constant defined for level: " + level);
        }
    }


    JavaEscapeLevel(final int escapeLevel) {
        this.escapeLevel = escapeLevel;
    }

    /**
     * Return the int escape level.
     *
     * @return the escape level.
     */
    public int getEscapeLevel() {
        return this.escapeLevel;
    }

}