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 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package javax.lang.model;

import java.util.Collections;
import java.util.Set;
import java.util.HashSet;

/**
 * Source versions of the Java™ programming language.
 *
 * See the appropriate edition of
 * <cite>The Java&trade; Language Specification</cite>
 * for information about a particular source version.
 *
 * <p>Note that additional source version constants will be added to
 * model future releases of the language.
 *
 * @author Joseph D. Darcy
 * @author Scott Seligman
 * @author Peter von der Ah&eacute;
 * @since 1.6
 */
public enum SourceVersion {
 /*
 * Summary of language evolution
 * 1.1: nested classes
 * 1.2: strictfp
 * 1.3: no changes
 * 1.4: assert
 * 1.5: annotations, generics, autoboxing, var-args...
 * 1.6: no changes
 * 1.7: diamond syntax, try-with-resources, etc.
 * 1.8: lambda expressions and default methods
 */

 /**
 * The original version.
 *
 * The language described in
 * <cite>The Java&trade; Language Specification, First Edition</cite>.
 */
 RELEASE_0,

 /**
 * The version recognized by the Java Platform 1.1.
 *
 * The language is {@code RELEASE_0} augmented with nested classes as described in the 1.1 update to
 * <cite>The Java&trade; Language Specification, First Edition</cite>.
 */
 RELEASE_1,

 /**
 * The version recognized by the Java 2 Platform, Standard Edition,
 * v 1.2.
 *
 * The language described in
 * <cite>The Java&trade; Language Specification,
 * Second Edition</cite>, which includes the {@code
 * strictfp} modifier.
 */
 RELEASE_2,

 /**
 * The version recognized by the Java 2 Platform, Standard Edition,
 * v 1.3.
 *
 * No major changes from {@code RELEASE_2}.
 */
 RELEASE_3,

 /**
 * The version recognized by the Java 2 Platform, Standard Edition,
 * v 1.4.
 *
 * Added a simple assertion facility.
 */
 RELEASE_4,

 /**
 * The version recognized by the Java 2 Platform, Standard
 * Edition 5.0.
 *
 * The language described in
 * <cite>The Java&trade; Language Specification,
 * Third Edition</cite>. First release to support
 * generics, annotations, autoboxing, var-args, enhanced {@code
 * for} loop, and hexadecimal floating-point literals.
 */
 RELEASE_5,

 /**
 * The version recognized by the Java Platform, Standard Edition
 * 6.
 *
 * No major changes from {@code RELEASE_5}.
 */
 RELEASE_6,

 /**
 * The version recognized by the Java Platform, Standard Edition
 * 7.
 *
 * Additions in this release include, diamond syntax for
 * constructors, {@code try}-with-resources, strings in switch,
 * binary literals, and multi-catch.
 * @since 1.7
 */
 RELEASE_7,

 /**
 * The version recognized by the Java Platform, Standard Edition
 * 8.
 *
 * Additions in this release include lambda expressions and default methods.
 * @since 1.8
 */
 RELEASE_8;

 // Note that when adding constants for newer releases, the
 // behavior of latest() and latestSupported() must be updated too.

 /**
 * Returns the latest source version that can be modeled.
 *
 * @return the latest source version that can be modeled
 */
 public static SourceVersion latest() {
 return RELEASE_8;
 }

 private static final SourceVersion latestSupported = getLatestSupported();

 private static SourceVersion getLatestSupported() {
 try {
 String specVersion = System.getProperty("java.specification.version");

 if ("1.8".equals(specVersion))
 return RELEASE_8;
 else if("1.7".equals(specVersion))
 return RELEASE_7;
 else if("1.6".equals(specVersion))
 return RELEASE_6;
 } catch (SecurityException se) {}

 return RELEASE_5;
 }

 /**
 * Returns the latest source version fully supported by the
 * current execution environment. {@code RELEASE_5} or later must
 * be returned.
 *
 * @return the latest source version that is fully supported
 */
 public static SourceVersion latestSupported() {
 return latestSupported;
 }

 /**
 * Returns whether or not {@code name} is a syntactically valid
 * identifier (simple name) or keyword in the latest source
 * version. The method returns {@code true} if the name consists
 * of an initial character for which {@link
 * Character#isJavaIdentifierStart(int)} returns {@code true},
 * followed only by characters for which {@link
 * Character#isJavaIdentifierPart(int)} returns {@code true}.
 * This pattern matches regular identifiers, keywords, and the
 * literals {@code "true"}, {@code "false"}, and {@code "null"}.
 * The method returns {@code false} for all other strings.
 *
 * @param name the string to check
 * @return {@code true} if this string is a
 * syntactically valid identifier or keyword, {@code false}
 * otherwise.
 */
 public static boolean isIdentifier(CharSequence name) {
 String id = name.toString();

 if (id.length() == 0) {
 return false;
 }
 int cp = id.codePointAt(0);
 if (!Character.isJavaIdentifierStart(cp)) {
 return false;
 }
 for (int i = Character.charCount(cp);
 i < id.length();
 i += Character.charCount(cp)) {
 cp = id.codePointAt(i);
 if (!Character.isJavaIdentifierPart(cp)) {
 return false;
 }
 }
 return true;
 }

 /**
 * Returns whether or not {@code name} is a syntactically valid
 * qualified name in the latest source version. Unlike {@link
 * #isIdentifier isIdentifier}, this method returns {@code false}
 * for keywords and literals.
 *
 * @param name the string to check
 * @return {@code true} if this string is a
 * syntactically valid name, {@code false} otherwise.
 * @jls 6.2 Names and Identifiers
 */
 public static boolean isName(CharSequence name) {
 String id = name.toString();

 for(String s : id.split("\\.", -1)) {
 if (!isIdentifier(s) || isKeyword(s))
 return false;
 }
 return true;
 }

 private final static Set<String> keywords;
 static {
 Set<String> s = new HashSet<String>();
 String [] kws = {
 "abstract", "continue", "for", "new", "switch",
 "assert", "default", "if", "package", "synchronized",
 "boolean", "do", "goto", "private", "this",
 "break", "double", "implements", "protected", "throw",
 "byte", "else", "import", "public", "throws",
 "case", "enum", "instanceof", "return", "transient",
 "catch", "extends", "int", "short", "try",
 "char", "final", "interface", "static", "void",
 "class", "finally", "long", "strictfp", "volatile",
 "const", "float", "native", "super", "while",
 // literals
 "null", "true", "false"
 };
 for(String kw : kws)
 s.add(kw);
 keywords = Collections.unmodifiableSet(s);
 }

 /**
 * Returns whether or not {@code s} is a keyword or literal in the
 * latest source version.
 *
 * @param s the string to check
 * @return {@code true} if {@code s} is a keyword or literal, {@code false} otherwise.
 */
 public static boolean isKeyword(CharSequence s) {
 String keywordOrLiteral = s.toString();
 return keywords.contains(keywordOrLiteral);
 }
}