Java tutorial
/** * 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 java.util.Collections; import java.util.Iterator; import java.util.List; /** * <p> * A {@code DiffResult} contains a collection of the differences between two * {@link Diffable} objects. Typically these differences are displayed using * {@link #toString()} method, which returns a string describing the fields that * differ between the objects. * </p> * <p> * Use a {@link DiffBuilder} to build a {@code DiffResult} comparing two objects. * </p> * * @since 3.3 * @version $Id$ */ public class DiffResult implements Iterable<Diff<?>> { /** * <p> * The {@code String} returned when the objects have no differences: * {@value} * </p> */ public static final String OBJECTS_SAME_STRING = ""; private static final String DIFFERS_STRING = "differs from"; private final List<Diff<?>> diffs; private final Object lhs; private final Object rhs; private final ToStringStyle style; /** * <p> * Creates a {@link DiffResult} containing the differences between two * objects. * </p> * * @param lhs * the left hand object * @param rhs * the right hand object * @param diffs * the list of differences, may be empty * @param style * the style to use for the {@link #toString()} method. May be * {@code null}, in which case * {@link ToStringStyle#DEFAULT_STYLE} is used * @throws IllegalArgumentException * if {@code lhs}, {@code rhs} or {@code diffs} is {@code null} */ DiffResult(final Object lhs, final Object rhs, final List<Diff<?>> diffs, final ToStringStyle style) { if (lhs == null) { throw new IllegalArgumentException("Left hand object cannot be null"); } if (rhs == null) { throw new IllegalArgumentException("Right hand object cannot be null"); } if (diffs == null) { throw new IllegalArgumentException("List of differences cannot be null"); } this.diffs = diffs; this.lhs = lhs; this.rhs = rhs; if (style == null) { this.style = ToStringStyle.DEFAULT_STYLE; } else { this.style = style; } } /** * <p> * Returns an unmodifiable list of {@code Diff}s. The list may be empty if * there were no differences between the objects. * </p> * * @return an unmodifiable list of {@code Diff}s */ public List<Diff<?>> getDiffs() { return Collections.unmodifiableList(diffs); } /** * <p> * Returns the number of differences between the two objects. * </p> * * @return the number of differences */ public int getNumberOfDiffs() { return diffs.size(); } /** * <p> * Returns the style used by the {@link #toString()} method. * </p> * * @return the style */ public ToStringStyle getToStringStyle() { return style; } /** * <p> * Builds a {@code String} description of the differences contained within * this {@code DiffResult}. A {@link ToStringBuilder} is used for each object * and the style of the output is governed by the {@code ToStringStyle} * passed to the constructor. * </p> * * <p> * If there are no differences stored in this list, the method will return * {@link #OBJECTS_SAME_STRING}. Otherwise, using the example given in * {@link Diffable} and {@link ToStringStyle#SHORT_PREFIX_STYLE}, an output * might be: * </p> * * <pre> * Person[name=John Doe,age=32] differs from Person[name=Joe Bloggs,age=26] * </pre> * * <p> * This indicates that the objects differ in name and age, but not in * smoking status. * </p> * * <p> * To use a different {@code ToStringStyle} for an instance of this class, * use {@link #toString(ToStringStyle)}. * </p> * * @return a {@code String} description of the differences. */ @Override public String toString() { return toString(style); } /** * <p> * Builds a {@code String} description of the differences contained within * this {@code DiffResult}, using the supplied {@code ToStringStyle}. * </p> * * @param style * the {@code ToStringStyle} to use when outputting the objects * * @return a {@code String} description of the differences. */ public String toString(final ToStringStyle style) { if (diffs.size() == 0) { return OBJECTS_SAME_STRING; } final ToStringBuilder lhsBuilder = new ToStringBuilder(lhs, style); final ToStringBuilder rhsBuilder = new ToStringBuilder(rhs, style); for (final Diff<?> diff : diffs) { lhsBuilder.append(diff.getFieldName(), diff.getLeft()); rhsBuilder.append(diff.getFieldName(), diff.getRight()); } return String.format("%s %s %s", lhsBuilder.build(), DIFFERS_STRING, rhsBuilder.build()); } /** * <p> * Returns an iterator over the {@code Diff} objects contained in this list. * </p> * * @return the iterator */ @Override public Iterator<Diff<?>> iterator() { return diffs.iterator(); } }