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Apache Commons Lang, a package of Java utility classes for the classes that are in java.lang's hierarchy, or are considered to be so standard as to justify existence in java.lang.
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/*
 * 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.builder;

import org.apache.commons.lang3.ClassUtils;
import org.apache.commons.lang3.StringUtils;

/**
 * Works with {@link ToStringBuilder} to create a "deep" {@code toString}.
 * But instead a single line like the {@link RecursiveToStringStyle} this creates a multiline String
 * similar to the {@link ToStringStyle#MULTI_LINE_STYLE}.
 *
 * To use this class write code as follows:
 *
 *  * public class Job {
 *   String title;
 *   ...
 * }
 *
 * public class Person {
 *   String name;
 *   int age;
 *   boolean smoker;
 *   Job job;
 *
 *   ...
 *
 *   public String toString() {
 *     return new ReflectionToStringBuilder(this, new MultilineRecursiveToStringStyle()).toString();
 *   }
 * }
 * 
 *
 * 
 * This will produce a toString of the format:

 * {@code Person@7f54[ 

 *   name=Stephen, 

 *   age=29, 

 *   smokealse, 

 *   job=Job@43cd2[ 

 *     title=Manager 

 *    ] 

 * ]
 * }
 * 
 *
 * @since 3.4
 */
public class MultilineRecursiveToStringStyle extends RecursiveToStringStyle {

    /**
     * Required for serialization support.
     * @see java.io.Serializable
     */
    private static final long serialVersionUID = 1L;

    /** Indenting of inner lines. */
    private static final int INDENT = 2;

    /** Current indenting. */
    private int spaces = 2;

    /**
     * Constructs a new instance.
     */
    public MultilineRecursiveToStringStyle() {
        resetIndent();
    }

    @Override
    protected void appendDetail(final StringBuffer buffer, final String fieldName, final boolean[] array) {
        spaces += INDENT;
        resetIndent();
        super.appendDetail(buffer, fieldName, array);
        spaces -= INDENT;
        resetIndent();
    }

    @Override
    protected void appendDetail(final StringBuffer buffer, final String fieldName, final byte[] array) {
        spaces += INDENT;
        resetIndent();
        super.appendDetail(buffer, fieldName, array);
        spaces -= INDENT;
        resetIndent();
    }

    @Override
    protected void appendDetail(final StringBuffer buffer, final String fieldName, final char[] array) {
        spaces += INDENT;
        resetIndent();
        super.appendDetail(buffer, fieldName, array);
        spaces -= INDENT;
        resetIndent();
    }

    @Override
    protected void appendDetail(final StringBuffer buffer, final String fieldName, final double[] array) {
        spaces += INDENT;
        resetIndent();
        super.appendDetail(buffer, fieldName, array);
        spaces -= INDENT;
        resetIndent();
    }

    @Override
    protected void appendDetail(final StringBuffer buffer, final String fieldName, final float[] array) {
        spaces += INDENT;
        resetIndent();
        super.appendDetail(buffer, fieldName, array);
        spaces -= INDENT;
        resetIndent();
    }

    @Override
    protected void appendDetail(final StringBuffer buffer, final String fieldName, final int[] array) {
        spaces += INDENT;
        resetIndent();
        super.appendDetail(buffer, fieldName, array);
        spaces -= INDENT;
        resetIndent();
    }

    @Override
    protected void appendDetail(final StringBuffer buffer, final String fieldName, final long[] array) {
        spaces += INDENT;
        resetIndent();
        super.appendDetail(buffer, fieldName, array);
        spaces -= INDENT;
        resetIndent();
    }

    @Override
    public void appendDetail(final StringBuffer buffer, final String fieldName, final Object value) {
        if (!ClassUtils.isPrimitiveWrapper(value.getClass()) && !String.class.equals(value.getClass())
                && accept(value.getClass())) {
            spaces += INDENT;
            resetIndent();
            buffer.append(ReflectionToStringBuilder.toString(value, this));
            spaces -= INDENT;
            resetIndent();
        } else {
            super.appendDetail(buffer, fieldName, value);
        }
    }

    @Override
    protected void appendDetail(final StringBuffer buffer, final String fieldName, final Object[] array) {
        spaces += INDENT;
        resetIndent();
        super.appendDetail(buffer, fieldName, array);
        spaces -= INDENT;
        resetIndent();
    }

    @Override
    protected void appendDetail(final StringBuffer buffer, final String fieldName, final short[] array) {
        spaces += INDENT;
        resetIndent();
        super.appendDetail(buffer, fieldName, array);
        spaces -= INDENT;
        resetIndent();
    }

    @Override
    protected void reflectionAppendArrayDetail(final StringBuffer buffer, final String fieldName, final Object array) {
        spaces += INDENT;
        resetIndent();
        super.reflectionAppendArrayDetail(buffer, fieldName, array);
        spaces -= INDENT;
        resetIndent();
    }

    /**
     * Resets the fields responsible for the line breaks and indenting.
     * Must be invoked after changing the {@link #spaces} value.
     */
    private void resetIndent() {
        setArrayStart("{" + System.lineSeparator() + spacer(spaces));
        setArraySeparator("," + System.lineSeparator() + spacer(spaces));
        setArrayEnd(System.lineSeparator() + spacer(spaces - INDENT) + "}");

        setContentStart("[" + System.lineSeparator() + spacer(spaces));
        setFieldSeparator("," + System.lineSeparator() + spacer(spaces));
        setContentEnd(System.lineSeparator() + spacer(spaces - INDENT) + "]");
    }

    /**
     * Creates a StringBuilder responsible for the indenting.
     *
     * @param spaces how far to indent
     * @return a StringBuilder with {spaces} leading space characters.
     */
    private String spacer(final int spaces) {
        return StringUtils.repeat(' ', spaces);
    }

}