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Ant example source code file (EnumeratedAttribute.java)

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

Java - Ant tags/keywords

buildexception, buildexception, class, enumeratedattribut, enumeratedattribut, enumeratedattribute, enumeratedattribute, exception, string, string, you

The EnumeratedAttribute.java source code

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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 org.apache.tools.ant.types;

import org.apache.tools.ant.BuildException;

/**
 * Helper class for attributes that can only take one of a fixed list
 * of values.
 *
 * <p>See {@link org.apache.tools.ant.taskdefs.FixCRLF FixCRLF} for an
 * example.
 *
 */
public abstract class EnumeratedAttribute {
    // CheckStyle:VisibilityModifier OFF - bc
    /**
     * The selected value in this enumeration.
     */
    protected String value;

    // CheckStyle:VisibilityModifier ON

    /**
     * the index of the selected value in the array.
     */
    private int index = -1;

    /**
     * This is the only method a subclass needs to implement.
     *
     * @return an array holding all possible values of the enumeration.
     * The order of elements must be fixed so that <tt>indexOfValue(String)
     * always return the same index for the same value.
     */
    public abstract String[] getValues();

    /** bean constructor */
    protected EnumeratedAttribute() {
    }

    /**
     * Factory method for instantiating EAs via API in a more
     * developer friendly way.
     * @param clazz             Class, extending EA, which to instantiate
     * @param value             The value to set on that EA
     * @return                  Configured EA
     * @throws BuildException   If the class could not be found or the value
     *                          is not valid for the given EA-class.
     * @see <a href="http://issues.apache.org/bugzilla/show_bug.cgi?id=14831">
     * http://issues.apache.org/bugzilla/show_bug.cgi?id=14831</a>
     */
    public static EnumeratedAttribute getInstance(
        Class/*<? extends EnumeratedAttribute>*/ clazz,
        String value) throws BuildException {
        if (!EnumeratedAttribute.class.isAssignableFrom(clazz)) {
            throw new BuildException(
                "You have to provide a subclass from EnumeratedAttribut as clazz-parameter.");
        }
        EnumeratedAttribute ea = null;
        try {
            ea = (EnumeratedAttribute) clazz.newInstance();
        } catch (Exception e) {
            throw new BuildException(e);
        }
        ea.setValue(value);
        return ea;
    }

    /**
     * Invoked by {@link org.apache.tools.ant.IntrospectionHelper IntrospectionHelper}.
     * @param value the <code>String value of the attribute
     * @throws BuildException if the value is not valid for the attribute
     */
    public final void setValue(String value) throws BuildException {
        int idx = indexOfValue(value);
        if (idx == -1) {
            throw new BuildException(value + " is not a legal value for this attribute");
        }
        this.index = idx;
        this.value = value;
    }

    /**
     * Is this value included in the enumeration?
     * @param value the <code>String value to look up
     * @return true if the value is valid
     */
    public final boolean containsValue(String value) {
        return (indexOfValue(value) != -1);
    }

    /**
     * get the index of a value in this enumeration.
     * @param value the string value to look for.
     * @return the index of the value in the array of strings
     * or -1 if it cannot be found.
     * @see #getValues()
     */
    public final int indexOfValue(String value) {
        String[] values = getValues();
        if (values == null || value == null) {
            return -1;
        }
        for (int i = 0; i < values.length; i++) {
            if (value.equals(values[i])) {
                return i;
            }
        }
        return -1;
    }

    /**
     * @return the selected value.
     */
    public final String getValue() {
        return value;
    }

    /**
     * @return the index of the selected value in the array.
     * @see #getValues()
     */
    public final int getIndex() {
        return index;
    }

    /**
     * Convert the value to its string form.
     *
     * @return the string form of the value.
     */
    public String toString() {
        return getValue();
    }

}

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