* Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

import java.nio.charset.Charset;

import java.nio.charset.spi.CharsetProvider;

import java.util.Iterator;

import java.util.Locale;

import java.util.Map;

import java.security.AccessController;

import java.security.PrivilegedAction;

public class StandardCharsets extends CharsetProvider {

    // Maps canonical names to class names

    private Map<String,String> classMap;

    // Maps alias names to canonical names

    private Map<String,String> aliasMap;

    // Maps canonical names to cached instances

    private Map<String,Charset> cache;

    private String packagePrefix = "sun.nio.cs";

        this.aliasMap = new Aliases();

        this.classMap = new Classes();

        this.cache = new Cache();

    }

    private String canonicalize(String csn) {

        String acn = aliasMap.get(csn);

        return (acn != null) ? acn : csn;

    }

    // Private ASCII-only version, optimized for interpretation during startup

    //

    private static String toLower(String s) {

        int n = s.length();

        boolean allLower = true;

        for (int i = 0; i < n; i++) {

            int c = s.charAt(i);

            if (((c - 'A') | ('Z' - c)) >= 0) {

                allLower = false;

                break;

            }

        }

        if (allLower)

            return s;

        char[] ca = new char[n];

        for (int i = 0; i < n; i++) {

            int c = s.charAt(i);

            if (((c - 'A') | ('Z' - c)) >= 0)

                ca[i] = (char)(c + 0x20);

            else

                ca[i] = (char)c;

        }

        return new String(ca);

    }

    private Charset lookup(String charsetName) {

        init();

        String csn = canonicalize(toLower(charsetName));

        // Check cache first

        Charset cs = cache.get(csn);

        if (cs != null)

            return cs;

        // Do we even support this charset?

        String cln = classMap.get(csn);

        if (cln == null)

            return null;

        if (cln.equals("US_ASCII")) {

            cs = new US_ASCII();

            cache.put(csn, cs);

            return cs;

        }

        // Instantiate the charset and cache it

        try {

            Class<?> c = Class.forName(packagePrefix + "." + cln,

                                    true,

                                    this.getClass().getClassLoader());

            cs = (Charset)c.newInstance();

            cache.put(csn, cs);

            return cs;

        } catch (ClassNotFoundException |

                 IllegalAccessException |

                 InstantiationException x) {

            return null;

        }

    public final Charset charsetForName(String charsetName) {

        synchronized (this) {

            return lookup(canonicalize(charsetName));

        }

    }

    public final Iterator<Charset> charsets() {

        synchronized (this) {

            init();

        }

        return new Iterator<Charset>() {

                Iterator<String> i = classMap.keySet().iterator();

                public boolean hasNext() {

                    return i.hasNext();

                }

                public Charset next() {

                    String csn = i.next();

                    return lookup(csn);

                }

                public void remove() {

                    throw new UnsupportedOperationException();

                }

            };

    }

    private boolean initialized = false;

    /*   provider the sun.nio.cs.map property fir sjis/ms932 mapping hack 

     */

    private void init() {

        if (initialized)

            return;

        if (!sun.misc.VM.isBooted())

            return;

        initialized = true;

        String map = getProperty("sun.nio.cs.map");

        if (map != null) {

            String[] maps = map.split(",");

            for (int i = 0; i < maps.length; i++) {

                if (maps[i].equalsIgnoreCase("Windows-31J/Shift_JIS")) {

                    // if we dont have both sjis and ms932, do nothing

                    if (classMap.get("shift_jis") == null ||

                        classMap.get("windows-31j") == null) {

                        break;

                    }

                    aliases_MS932 = new String[] {

                        "MS932",        // JDK historical

                        "windows-932",

                        "csWindows31J",

                        "shift-jis",

                        "ms_kanji",

                        "x-sjis",

                        "csShiftJIS",

                        // This alias takes precedence over the actual

                        // Shift_JIS charset itself since aliases are always

                        // resolved first, before looking up canonical names.

                        "shift_jis"

                    };

                    aliases_SJIS = new String[] { "sjis" };

                    for (String alias : aliases_MS932) {

                        aliasMap.put(toLower(alias), "windows-31j");

                    }

                    cache.put("shift_jis", null);

                    break;

                }

            }

        }

    }

    private static String getProperty(String key) {

        // this method may be called during initialization of

        // system class loader and thus not using lambda

        return AccessController.doPrivileged(

            new PrivilegedAction<String>() {

                @Override

                public String run() {

                    return System.getProperty(key);

                }

            });

    }