* Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.

import com.sun.org.apache.bcel.internal.Const;

import java.io.DataInput;

import java.io.DataOutputStream;

import java.io.IOException;

import java.util.HashMap;

import java.util.LinkedHashMap;

import java.util.Map;

 * This class is derived from the abstract {@link Constant}

 * @version $Id: ConstantUtf8.java 1750029 2016-06-23 22:14:38Z sebb $

    private final String bytes;

    // TODO these should perhaps be AtomicInt?

    private static volatile int considered = 0;

    private static volatile int hits = 0;

    private static volatile int skipped = 0;

    private static volatile int created = 0;

    // Set the size to 0 or below to skip caching entirely

    private static final int MAX_CACHED_SIZE = 200;

    private static final boolean BCEL_STATISTICS = false;

    private static class CACHE_HOLDER {

        private static final int MAX_CACHE_ENTRIES = 20000;

        private static final int INITIAL_CACHE_CAPACITY = (int)(MAX_CACHE_ENTRIES/0.75);

        private static final HashMap<String, ConstantUtf8> CACHE =

                new LinkedHashMap<String, ConstantUtf8>(INITIAL_CACHE_CAPACITY, 0.75f, true) {

            private static final long serialVersionUID = -8506975356158971766L;

            @Override

            protected boolean removeEldestEntry(final Map.Entry<String, ConstantUtf8> eldest) {

                 return size() > MAX_CACHE_ENTRIES;

            }

        };

    }

    // for accesss by test code

    static void printStats() {

        System.err.println("Cache hit " + hits + "/" + considered +", " + skipped + " skipped");

        System.err.println("Total of " + created + " ConstantUtf8 objects created");

    }

    // for accesss by test code

    static void clearStats() {

        hits = considered = skipped = created = 0;

    }

    static {

        if (BCEL_STATISTICS) {

            Runtime.getRuntime().addShutdownHook(new Thread() {

                @Override

                public void run() {

                    printStats();

                }

            });

        }

    }

    /**

     * @since 6.0

     */

    public static ConstantUtf8 getCachedInstance(final String s) {

        if (s.length() > MAX_CACHED_SIZE) {

            skipped++;

            return  new ConstantUtf8(s);

        }

        considered++;

        synchronized (ConstantUtf8.class) { // might be better with a specific lock object

            ConstantUtf8 result = CACHE_HOLDER.CACHE.get(s);

            if (result != null) {

                    hits++;

                    return result;

                }

            result = new ConstantUtf8(s);

            CACHE_HOLDER.CACHE.put(s, result);

            return result;

        }

    }

    /**

     * @since 6.0

     */

    public static ConstantUtf8 getInstance(final String s) {

        return new ConstantUtf8(s);

    }

    /**

     * @since 6.0

     */

    public static ConstantUtf8 getInstance (final DataInput input)  throws IOException {

        return getInstance(input.readUTF());

    }

    /**

     * Initialize from another object.

     */

    public ConstantUtf8(final ConstantUtf8 c) {

        this(c.getBytes());

    }

    /**

     * Initialize instance from file data.

     *

     * @param file Input stream

     * @throws IOException

     */

    ConstantUtf8(final DataInput file) throws IOException {

        super(Const.CONSTANT_Utf8);

        bytes = file.readUTF();

        created++;

    }

    /**

     * @param bytes Data

     */

    public ConstantUtf8(final String bytes) {

        super(Const.CONSTANT_Utf8);

        if (bytes == null) {

            throw new IllegalArgumentException("bytes must not be null!");

        }

        this.bytes = bytes;

        created++;

    }

    /**

     * Called by objects that are traversing the nodes of the tree implicitely

     * defined by the contents of a Java class. I.e., the hierarchy of methods,

     * fields, attributes, etc. spawns a tree of objects.

     *

     * @param v Visitor object

     */

    @Override

    public void accept( final Visitor v ) {

        v.visitConstantUtf8(this);

    }

    /**

     * Dump String in Utf8 format to file stream.

     *

     * @param file Output file stream

     * @throws IOException

     */

    @Override

    public final void dump( final DataOutputStream file ) throws IOException {

        file.writeByte(super.getTag());

        file.writeUTF(bytes);

    }

    /**

     * @return Data converted to string.

     */

    public final String getBytes() {

        return bytes;

    }

    /**

     * @param bytes the raw bytes of this Utf-8

     * @deprecated (since 6.0)

     */

    @java.lang.Deprecated

    public final void setBytes( final String bytes ) {

        throw new UnsupportedOperationException();

    }

    /**

     * @return String representation

     */

    @Override

    public final String toString() {

        return super.toString() + "(\"" + Utility.replace(bytes, "\n", "\\n") + "\")";

    }