Java Number Format Pattern getNumber(final Map map, final Object key)

Description

Gets a Number from a Map in a null-safe manner.

License

Apache License

Parameter

Parameter	Description
map	the map to use
key	the key to look up

Return

the value in the Map as a Number, null if null map input

Declaration

public static Number getNumber(final Map map, final Object key) 

Method Source Code

//package com.java2s;
/*//from  w ww.jav  a  2s  .c om
 *  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.
 */

import java.text.NumberFormat;
import java.text.ParseException;

import java.util.Map;

public class Main {
    /**
     * Gets a Number from a Map in a null-safe manner.
     * <p>
     * If the value is a <code>Number</code> it is returned directly.
     * If the value is a <code>String</code> it is converted using
     * {@link NumberFormat#parse(String)} on the system default formatter
     * returning <code>null</code> if the conversion fails.
     * Otherwise, <code>null</code> is returned.
     *
     * @param map  the map to use
     * @param key  the key to look up
     * @return the value in the Map as a Number, <code>null</code> if null map input
     */
    public static Number getNumber(final Map map, final Object key) {
        if (map != null) {
            Object answer = map.get(key);
            if (answer != null) {
                if (answer instanceof Number) {
                    return (Number) answer;

                } else if (answer instanceof String) {
                    try {
                        String text = (String) answer;
                        return NumberFormat.getInstance().parse(text);

                    } catch (ParseException e) {
                        // failure means null is returned
                    }
                }
            }
        }
        return null;
    }

    /**
     *  Looks up the given key in the given map, converting the result into
     *  a number, using the default value if the the conversion fails.
     *
     *  @param map  the map whose value to look up
     *  @param key  the key of the value to look up in that map
     *  @param defaultValue  what to return if the value is null or if the
     *     conversion fails
     *  @return  the value in the map as a number, or defaultValue if the 
     *    original value is null, the map is null or the number conversion
     *    fails
     */
    public static Number getNumber(Map map, Object key, Number defaultValue) {
        Number answer = getNumber(map, key);
        if (answer == null) {
            answer = defaultValue;
        }
        return answer;
    }
}

Related

1. getIntegerFormat()
2. getIntegerFormat(int maximumIntegerDigits)
3. getIntegerFormatter()
4. getIntegerNumberFormat()
5. getNeptusIntegerFormat()
6. getNumberComma(String number)
7. getNumberFormat()
8. getNumberFormat()
9. getNumberFormat(BigDecimal num, final int digits)