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Java example source code file (NameGenerator.java)

This example Java source code file (NameGenerator.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

array, class, identityhashmap, integer, map, namegenerator, string, suppresswarnings, util

The NameGenerator.java Java example source code

/*
 * Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package java.beans;

import java.util.HashMap;
import java.util.IdentityHashMap;
import java.util.Map;

import static java.util.Locale.ENGLISH;

/**
 * A utility class which generates unique names for object instances.
 * The name will be a concatenation of the unqualified class name
 * and an instance number.
 * <p>
 * For example, if the first object instance javax.swing.JButton
 * is passed into <code>instanceName then the returned
 * string identifier will be "JButton0".
 *
 * @author Philip Milne
 */
class NameGenerator {

    private Map<Object, String> valueToName;
    private Map<String, Integer> nameToCount;

    public NameGenerator() {
        valueToName = new IdentityHashMap<>();
        nameToCount = new HashMap<>();
    }

    /**
     * Clears the name cache. Should be called to near the end of
     * the encoding cycle.
     */
    public void clear() {
        valueToName.clear();
        nameToCount.clear();
    }

    /**
     * Returns the root name of the class.
     */
    @SuppressWarnings("rawtypes")
    public static String unqualifiedClassName(Class type) {
        if (type.isArray()) {
            return unqualifiedClassName(type.getComponentType())+"Array";
        }
        String name = type.getName();
        return name.substring(name.lastIndexOf('.')+1);
    }

    /**
     * Returns a String which capitalizes the first letter of the string.
     */
    public static String capitalize(String name) {
        if (name == null || name.length() == 0) {
            return name;
        }
        return name.substring(0, 1).toUpperCase(ENGLISH) + name.substring(1);
    }

    /**
     * Returns a unique string which identifies the object instance.
     * Invocations are cached so that if an object has been previously
     * passed into this method then the same identifier is returned.
     *
     * @param instance object used to generate string
     * @return a unique string representing the object
     */
    public String instanceName(Object instance) {
        if (instance == null) {
            return "null";
        }
        if (instance instanceof Class) {
            return unqualifiedClassName((Class)instance);
        }
        else {
            String result = valueToName.get(instance);
            if (result != null) {
                return result;
            }
            Class<?> type = instance.getClass();
            String className = unqualifiedClassName(type);

            Integer size = nameToCount.get(className);
            int instanceNumber = (size == null) ? 0 : (size).intValue() + 1;
            nameToCount.put(className, new Integer(instanceNumber));

            result = className + instanceNumber;
            valueToName.put(instance, result);
            return result;
        }
    }
}

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