src/main/java/org/apache/commons/lang3/util/FormattableUtils.java

/*
 * 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.commons.lang3.util;

import static java.util.FormattableFlags.LEFT_JUSTIFY;

import java.util.Formattable;
import java.util.Formatter;

import org.apache.commons.lang3.ObjectUtils;
import org.apache.commons.lang3.Validate;

/**
 * Provides utilities for working with {@link Formattable}s.
 * 
 * @since Lang 3.0
 * @version $Id$
 */
public class FormattableUtils {

    private static final String SIMPLEST_FORMAT = "%1$s";

    /**
     * <p>{@link FormattableUtils} instances should NOT be constructed in
     * standard programming. Instead, the methods of the class should be invoked
     * statically.</p>
     * 
     * <p>This constructor is public to permit tools that require a JavaBean
     * instance to operate.</p>
     */
    public FormattableUtils() {
        super();
    }

    /**
     * Get the default formatted representation of the specified
     * {@link Formattable}.
     * 
     * @param formattable
     * @return String
     */
    public static String toString(Formattable formattable) {
        return String.format(SIMPLEST_FORMAT, formattable);
    }

    /**
     * Handles the common {@link Formattable} operations of truncate-pad-append,
     * with no ellipsis on precision overflow, and padding width underflow with
     * spaces.
     * 
     * @param seq to handle
     * @param formatter destination
     * @param flags for formatting
     * @param width of output
     * @param precision of output
     * @return {@code formatter}
     */
    public static Formatter append(CharSequence seq, Formatter formatter, int flags, int width,
            int precision) {
        return append(seq, formatter, flags, width, precision, ' ', null);
    }

    /**
     * Handles the common {@link Formattable} operations of truncate-pad-append,
     * with no ellipsis on precision overflow.
     * 
     * @param seq to handle
     * @param formatter destination
     * @param flags for formatting
     * @param width of output
     * @param precision of output
     * @param padChar to use
     * @return {@code formatter}
     */
    public static Formatter append(CharSequence seq, Formatter formatter, int flags, int width,
            int precision, char padChar) {
        return append(seq, formatter, flags, width, precision, padChar, null);
    }

    /**
     * Handles the common {@link Formattable} operations of truncate-pad-append,
     * padding width underflow with spaces.
     * 
     * @param seq to handle
     * @param formatter destination
     * @param flags for formatting
     * @param width of output
     * @param precision of output
     * @param ellipsis to use when precision dictates truncation; a {@code null}
     * or empty value causes a hard truncation
     * @return {@code formatter}
     */
    public static Formatter append(CharSequence seq, Formatter formatter, int flags, int width,
            int precision, CharSequence ellipsis) {
        return append(seq, formatter, flags, width, precision, ' ', ellipsis);
    }

    /**
     * Handles the common {@link Formattable} operations of truncate-pad-append.
     * 
     * @param seq to handle
     * @param formatter destination
     * @param flags for formatting
     * @param width of output
     * @param precision of output
     * @param padChar to use
     * @param ellipsis to use when precision dictates truncation; a {@code null}
     * or empty value causes a hard truncation
     * @return {@code formatter}
     */
    public static Formatter append(CharSequence seq, Formatter formatter, int flags, int width,
            int precision, char padChar, CharSequence ellipsis) {
        Validate.isTrue(ellipsis == null || precision < 0 || ellipsis.length() <= precision,
                "Specified ellipsis '%1$s' exceeds precision of %2$s", ellipsis, precision);
        StringBuilder buf = new StringBuilder(seq);
        if (precision >= 0 && precision < seq.length()) {
            CharSequence _ellipsis = ObjectUtils.defaultIfNull(ellipsis, "");
            buf.replace(precision - _ellipsis.length(), seq.length(), _ellipsis.toString());
        }
        boolean leftJustify = (flags & LEFT_JUSTIFY) == LEFT_JUSTIFY;
        for (int i = buf.length(); i < width; i++) {
            buf.insert(leftJustify ? i : 0, padChar);
        }
        formatter.format(buf.toString());
        return formatter;
    }
}