Data type conversion : Data Type Conversion « Data Type « Java Tutorial






/* 
 * 
 * The ObjectStyle Group Software License, version 1.1
 * ObjectStyle Group - http://objectstyle.org/
 * 
 * Copyright (c) 2002-2005, Andrei (Andrus) Adamchik and individual authors
 * of the software. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 
 * 3. The end-user documentation included with the redistribution, if any,
 *    must include the following acknowlegement:
 *    "This product includes software developed by independent contributors
 *    and hosted on ObjectStyle Group web site (http://objectstyle.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 * 
 * 4. The names "ObjectStyle Group" and "Cayenne" must not be used to endorse
 *    or promote products derived from this software without prior written
 *    permission. For written permission, email
 *    "andrus at objectstyle dot org".
 * 
 * 5. Products derived from this software may not be called "ObjectStyle"
 *    or "Cayenne", nor may "ObjectStyle" or "Cayenne" appear in their
 *    names without prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE OBJECTSTYLE GROUP OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * 
 * This software consists of voluntary contributions made by many
 * individuals and hosted on ObjectStyle Group web site.  For more
 * information on the ObjectStyle Group, please see
 * <http://objectstyle.org/>.
 */


import java.math.BigDecimal;
import java.math.BigInteger;


/**
 * A collection of static conversion utility methods.
 * 
 * @since 1.1
 * @author Andrei Adamchik
 */
public final class ConversionUtil {

    public static int toInt(Object object, int defaultValue) {
        if (object == null) {
            return defaultValue;
        }
        else if (object instanceof Number) {
            return ((Number) object).intValue();
        }
        else if (object instanceof String) {
            try {
                return Integer.parseInt((String) object);
            }
            catch (NumberFormatException ex) {
                return defaultValue;
            }
        }

        return defaultValue;
    }

    public static boolean toBoolean(Object object) {
        if (object instanceof Boolean) {
            return ((Boolean) object).booleanValue();
        }

        if (object instanceof Number) {
            return ((Number) object).intValue() != 0;
        }

        return object != null;
    }

    public static BigDecimal toBigDecimal(Object object) {

        if (object == null) {
            return null;
        }
        else if (object instanceof BigDecimal) {
            return (BigDecimal) object;
        }
        else if (object instanceof BigInteger) {
            return new BigDecimal((BigInteger) object);
        }
        else if (object instanceof Number) {
            return new BigDecimal(((Number) object).doubleValue());
        }

        throw new Exception("Can't convert to BigDecimal: " + object);
    }

    /**
     * Attempts to convert an object to Comparable instance.
     */
    public static Comparable toComparable(Object object) {
        if (object == null) {
            return null;
        }
        else if (object instanceof Comparable) {
            return (Comparable) object;
        }
        else if (object instanceof StringBuffer) {
            return object.toString();
        }
        else if (object instanceof char[]) {
            return new String((char[]) object);
        }
        else {
            throw new ClassCastException(
                "Invalid Comparable class:" + object.getClass().getName());
        }
    }

    /**
     * Attempts to convert an object to Comparable instance.
     */
    public static String toString(Object object) {
        if (object == null) {
            return null;
        }
        else if (object instanceof String) {
            return (String) object;
        }
        else if (object instanceof StringBuffer) {
            return object.toString();
        }
        else if (object instanceof char[]) {
            return new String((char[]) object);
        }
        else {
            throw new ClassCastException(
                "Invalid class for String conversion:" + object.getClass().getName());
        }
    }

    /**
     * Attempts to convert an object to an uppercase string.
     */
    public static Object toUpperCase(Object object) {
        if ((object instanceof String) || (object instanceof StringBuffer)) {
            return object.toString().toUpperCase();
        }
        else if (object instanceof char[]) {
            return new String((char[]) object).toUpperCase();
        }
        else {
            return object;
        }
    }

    private ConversionUtil() {
    }
}








2.16.Data Type Conversion
2.16.1.The Widening Conversion
2.16.2.The Narrowing Conversion
2.16.3.Narrowing conversion with information loss
2.16.4.An automatic type conversion
2.16.5.Casting Incompatible Types
2.16.6.Pass a string to the Integer class constructor and call the intValue()
2.16.7.Use toString method of Integer class to conver Integer into String.
2.16.8.Declaring Checked Exceptions
2.16.9.Automatic Type Promotion in Expressions
2.16.10.Convert byte array to Integer and Long
2.16.11.Class with methods for type conversion
2.16.12.Data type conversion
2.16.13.Convert primitive back and forth