com.google.gwt.dev.util.StringKey.java Source code

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Here is the source code for com.google.gwt.dev.util.StringKey.java

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/*
 * Copyright 2009 Google Inc.
 * 
 * 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 com.google.gwt.dev.util;

import java.io.Serializable;

/**
 * A "typed string" utility class that improves the readability of generic code
 * by using proper types. Equality and comparison are implemented by using both
 * the concrete type and string value.
 */
public abstract class StringKey implements Comparable<StringKey>, Serializable {

    /**
     * The hashcode is computed and stored since this type is expected to be used
     * as a map key.
     */
    private final int hashCode;
    private final String value;

    /**
     * Constructor. A <code>null</code> value is legal.
     * 
     * @param value the value this key object represents
     */
    protected StringKey(String value) {
        this.value = value;
        this.hashCode = getClass().getName().hashCode() * 13 + (value == null ? 0 : value.hashCode());
    }

    /**
     * Compares based on concrete type name and then value.
     */
    public final int compareTo(StringKey o) {
        if (getClass() == o.getClass()) {
            if (value == null) {
                return o.value == null ? 0 : -1;
            } else if (o.value == null) {
                return value == null ? 0 : 1;
            } else {
                return value.compareTo(o.value);
            }
        }
        return getClass().getName().compareTo(o.getClass().getName());
    }

    /**
     * Delegates to {@link #compareTo}.
     */
    @Override
    public final boolean equals(Object o) {
        if (o == null) {
            return false;
        }
        return compareTo((StringKey) o) == 0 ? true : false;
    }

    /**
     * Returns the value of the StringKey.
     */
    public final String get() {
        return value;
    }

    @Override
    public final int hashCode() {
        return hashCode;
    }

    /**
     * Delegates to {@link #get()}.
     */
    @Override
    public String toString() {
        return value;
    }
}