EqualsBuilder.java

/*
 * Copyright 2010 Daniel Bell
 *
 * Licensed 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 remixlab.util;

/**
 * <p>
 * Assists in implementing {@link Object#equals(Object)} methods.
 * </p>
 * <p>
 * <p>
 * This class provides methods to build a good equals method for any class. It follows
 * rules laid out in
 * <a href="http://java.sun.com/docs/books/effective/index.html">Effective Java</a> , by
 * Joshua Bloch. In particular the rule for comparing <code>doubles</code>,
 * <code>floats</code>, and arrays can be tricky. Also, making sure that
 * <code>equals()</code> and <code>hashCode()</code> are consistent can be difficult.
 * </p>
 * <p>
 * <p>
 * Two Objects that compare as equals must generate the same hash code, but two Objects
 * with the same hash code do not have to be equal.
 * </p>
 * <p>
 * <p>
 * All relevant fields should be included in the calculation of equals. Derived fields may
 * be ignored. In particular, any field used in generating a hash code must be used in the
 * equals method, and vice versa.
 * </p>
 * <p>
 * <p>
 * Typical use for the code is as follows:
 * </p>
 * <p>
 * <pre>
 * public boolean equals(Object obj) {
 *   if (obj == null) {
 *     return false;
 *   }
 *   if (obj == this) {
 *     return true;
 *   }
 *   if (obj.getClass() != getClass()) {
 *     return false;
 *   }
 *   MyClass rhs = (MyClass) obj;
 *   return new EqualsBuilder().appendSuper(super.equals(obj)).append(field1, rhs.field1).append(field2, rhs.field2)
 *       .append(field3, rhs.field3).isEquals();
 * }
 * </pre>
 * <p>
 * <p>
 * Alternatively, there is a method that uses reflection to determine the fields to test.
 * Because these fields are usually private, the method, <code>reflectionEquals</code>,
 * uses <code>AccessibleObject.setAccessible</code> to change the visibility of the
 * fields. This will fail under a security manager, unless the appropriate permissions are
 * set up correctly. It is also slower than testing explicitly.
 * </p>
 * <p>
 * <p>
 * A typical invocation for this method would look like:
 * </p>
 * <p>
 * <pre>
 * public boolean equals(Object obj) {
 *   return EqualsBuilder.reflectionEquals(this, obj);
 * }
 * </pre>
 *
 * @author Apache Software Foundation
 * @author <a href="mailto:steve.downey@netfolio.com">Steve Downey</a>
 * @author Gary Gregory
 * @author Pete Gieser
 * @author Arun Mammen Thomas
 * @author Oliver Sauder
 * @author Daniel Bell
 * @since 1.0
 */
public class EqualsBuilder {

  /**
   * If the fields tested are equals. The default value is <code>true</code>.
   */
  private boolean isEquals = true;

  /**
   * <p>
   * Constructor for EqualsBuilder.
   * </p>
   * <p>
   * <p>
   * Starts off assuming that equals is <code>true</code>.
   * </p>
   *
   * @see Object#equals(Object)
   */
  public EqualsBuilder() {
    // do nothing for now.
  }

  /**
   * <p>
   * Adds the result of <code>super.equals()</code> to this builder.
   * </p>
   *
   * @param superEquals the result of calling <code>super.equals()</code>
   * @return EqualsBuilder - used to chain calls.
   * @since 2.0
   */
  public EqualsBuilder appendSuper(boolean superEquals) {
    if (isEquals == false) {
      return this;
    }
    isEquals = superEquals;
    return this;
  }

  // -------------------------------------------------------------------------

  /**
   * <p>
   * Test if two <code>Object</code>s are equal using their <code>equals</code> method.
   * </p>
   *
   * @param lhs the left hand object
   * @param rhs the right hand object
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(Object lhs, Object rhs) {
    if (isEquals == false) {
      return this;
    }
    if (lhs == rhs) {
      return this;
    }
    if (lhs == null || rhs == null) {
      this.setEquals(false);
      return this;
    }
    Class<?> lhsClass = lhs.getClass();
    if (!lhsClass.isArray()) {
      // The simple case, not an array, just test the element
      isEquals = lhs.equals(rhs);
    } else if (lhs.getClass() != rhs.getClass()) {
      // Here when we compare different dimensions, for example: a boolean[][]
      // to a boolean[]
      this.setEquals(false);
    }
    // 'Switch' on type of array, to dispatch to the correct handler
    // This handles multi dimensional arrays of the same depth
    else if (lhs instanceof long[]) {
      append((long[]) lhs, (long[]) rhs);
    } else if (lhs instanceof int[]) {
      append((int[]) lhs, (int[]) rhs);
    } else if (lhs instanceof short[]) {
      append((short[]) lhs, (short[]) rhs);
    } else if (lhs instanceof char[]) {
      append((char[]) lhs, (char[]) rhs);
    } else if (lhs instanceof byte[]) {
      append((byte[]) lhs, (byte[]) rhs);
    } else if (lhs instanceof double[]) {
      append((double[]) lhs, (double[]) rhs);
    } else if (lhs instanceof float[]) {
      append((float[]) lhs, (float[]) rhs);
    } else if (lhs instanceof boolean[]) {
      append((boolean[]) lhs, (boolean[]) rhs);
    } else {
      // Not an array of primitives
      append((Object[]) lhs, (Object[]) rhs);
    }
    return this;
  }

  /**
   * <p>
   * Test if two <code>long</code> s are equal.
   * </p>
   *
   * @param lhs the left hand <code>long</code>
   * @param rhs the right hand <code>long</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(long lhs, long rhs) {
    if (isEquals == false) {
      return this;
    }
    isEquals = (lhs == rhs);
    return this;
  }

  /**
   * <p>
   * Test if two <code>int</code>s are equal.
   * </p>
   *
   * @param lhs the left hand <code>int</code>
   * @param rhs the right hand <code>int</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(int lhs, int rhs) {
    if (isEquals == false) {
      return this;
    }
    isEquals = (lhs == rhs);
    return this;
  }

  /**
   * <p>
   * Test if two <code>short</code>s are equal.
   * </p>
   *
   * @param lhs the left hand <code>short</code>
   * @param rhs the right hand <code>short</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(short lhs, short rhs) {
    if (isEquals == false) {
      return this;
    }
    isEquals = (lhs == rhs);
    return this;
  }

  /**
   * <p>
   * Test if two <code>char</code>s are equal.
   * </p>
   *
   * @param lhs the left hand <code>char</code>
   * @param rhs the right hand <code>char</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(char lhs, char rhs) {
    if (isEquals == false) {
      return this;
    }
    isEquals = (lhs == rhs);
    return this;
  }

  /**
   * <p>
   * Test if two <code>byte</code>s are equal.
   * </p>
   *
   * @param lhs the left hand <code>byte</code>
   * @param rhs the right hand <code>byte</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(byte lhs, byte rhs) {
    if (isEquals == false) {
      return this;
    }
    isEquals = (lhs == rhs);
    return this;
  }

  /**
   * <p>
   * Test if two <code>double</code>s are equal by testing that the pattern of bits
   * returned by <code>doubleToLong</code> are equal.
   * </p>
   * <p>
   * <p>
   * This handles NaNs, Infinities, and <code>-0.0</code>.
   * </p>
   * <p>
   * <p>
   * It is compatible with the hash code generated by <code>HashCodeBuilder</code>.
   * </p>
   *
   * @param lhs the left hand <code>double</code>
   * @param rhs the right hand <code>double</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(double lhs, double rhs) {
    if (isEquals == false) {
      return this;
    }
    return append(DoubleUtil.doubleToLongBits(lhs), DoubleUtil.doubleToLongBits(rhs));
  }

  /**
   * <p>
   * Test if two <code>float</code>s are equal byt testing that the pattern of bits
   * returned by doubleToLong are equal.
   * </p>
   * <p>
   * <p>
   * This handles NaNs, Infinities, and <code>-0.0</code>.
   * </p>
   * <p>
   * <p>
   * It is compatible with the hash code generated by <code>HashCodeBuilder</code>.
   * </p>
   *
   * @param lhs the left hand <code>float</code>
   * @param rhs the right hand <code>float</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(float lhs, float rhs) {
    if (isEquals == false) {
      return this;
    }
    return append(FloatUtil.floatToIntBits(lhs), FloatUtil.floatToIntBits(rhs));
  }

  /**
   * <p>
   * Test if two <code>booleans</code>s are equal.
   * </p>
   *
   * @param lhs the left hand <code>boolean</code>
   * @param rhs the right hand <code>boolean</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(boolean lhs, boolean rhs) {
    if (isEquals == false) {
      return this;
    }
    isEquals = (lhs == rhs);
    return this;
  }

  /**
   * <p>
   * Performs a deep comparison of two <code>Object</code> arrays.
   * </p>
   * <p>
   * <p>
   * This also will be called for the top level of multi-dimensional, ragged, and
   * multi-typed arrays.
   * </p>
   *
   * @param lhs the left hand <code>Object[]</code>
   * @param rhs the right hand <code>Object[]</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(Object[] lhs, Object[] rhs) {
    if (isEquals == false) {
      return this;
    }
    if (lhs == rhs) {
      return this;
    }
    if (lhs == null || rhs == null) {
      this.setEquals(false);
      return this;
    }
    if (lhs.length != rhs.length) {
      this.setEquals(false);
      return this;
    }
    for (int i = 0; i < lhs.length && isEquals; ++i) {
      append(lhs[i], rhs[i]);
    }
    return this;
  }

  /**
   * <p>
   * Deep comparison of array of <code>long</code>. Length and all values are compared.
   * </p>
   * <p>
   * <p>
   * The method {@link #append(long, long)} is used.
   * </p>
   *
   * @param lhs the left hand <code>long[]</code>
   * @param rhs the right hand <code>long[]</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(long[] lhs, long[] rhs) {
    if (isEquals == false) {
      return this;
    }
    if (lhs == rhs) {
      return this;
    }
    if (lhs == null || rhs == null) {
      this.setEquals(false);
      return this;
    }
    if (lhs.length != rhs.length) {
      this.setEquals(false);
      return this;
    }
    for (int i = 0; i < lhs.length && isEquals; ++i) {
      append(lhs[i], rhs[i]);
    }
    return this;
  }

  /**
   * <p>
   * Deep comparison of array of <code>int</code>. Length and all values are compared.
   * </p>
   * <p>
   * <p>
   * The method {@link #append(int, int)} is used.
   * </p>
   *
   * @param lhs the left hand <code>int[]</code>
   * @param rhs the right hand <code>int[]</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(int[] lhs, int[] rhs) {
    if (isEquals == false) {
      return this;
    }
    if (lhs == rhs) {
      return this;
    }
    if (lhs == null || rhs == null) {
      this.setEquals(false);
      return this;
    }
    if (lhs.length != rhs.length) {
      this.setEquals(false);
      return this;
    }
    for (int i = 0; i < lhs.length && isEquals; ++i) {
      append(lhs[i], rhs[i]);
    }
    return this;
  }

  /**
   * <p>
   * Deep comparison of array of <code>short</code>. Length and all values are compared.
   * </p>
   * <p>
   * <p>
   * The method {@link #append(short, short)} is used.
   * </p>
   *
   * @param lhs the left hand <code>short[]</code>
   * @param rhs the right hand <code>short[]</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(short[] lhs, short[] rhs) {
    if (isEquals == false) {
      return this;
    }
    if (lhs == rhs) {
      return this;
    }
    if (lhs == null || rhs == null) {
      this.setEquals(false);
      return this;
    }
    if (lhs.length != rhs.length) {
      this.setEquals(false);
      return this;
    }
    for (int i = 0; i < lhs.length && isEquals; ++i) {
      append(lhs[i], rhs[i]);
    }
    return this;
  }

  /**
   * <p>
   * Deep comparison of array of <code>char</code>. Length and all values are compared.
   * </p>
   * <p>
   * <p>
   * The method {@link #append(char, char)} is used.
   * </p>
   *
   * @param lhs the left hand <code>char[]</code>
   * @param rhs the right hand <code>char[]</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(char[] lhs, char[] rhs) {
    if (isEquals == false) {
      return this;
    }
    if (lhs == rhs) {
      return this;
    }
    if (lhs == null || rhs == null) {
      this.setEquals(false);
      return this;
    }
    if (lhs.length != rhs.length) {
      this.setEquals(false);
      return this;
    }
    for (int i = 0; i < lhs.length && isEquals; ++i) {
      append(lhs[i], rhs[i]);
    }
    return this;
  }

  /**
   * <p>
   * Deep comparison of array of <code>byte</code>. Length and all values are compared.
   * </p>
   * <p>
   * <p>
   * The method {@link #append(byte, byte)} is used.
   * </p>
   *
   * @param lhs the left hand <code>byte[]</code>
   * @param rhs the right hand <code>byte[]</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(byte[] lhs, byte[] rhs) {
    if (isEquals == false) {
      return this;
    }
    if (lhs == rhs) {
      return this;
    }
    if (lhs == null || rhs == null) {
      this.setEquals(false);
      return this;
    }
    if (lhs.length != rhs.length) {
      this.setEquals(false);
      return this;
    }
    for (int i = 0; i < lhs.length && isEquals; ++i) {
      append(lhs[i], rhs[i]);
    }
    return this;
  }

  /**
   * <p>
   * Deep comparison of array of <code>double</code>. Length and all values are compared.
   * </p>
   * <p>
   * <p>
   * The method {@link #append(double, double)} is used.
   * </p>
   *
   * @param lhs the left hand <code>double[]</code>
   * @param rhs the right hand <code>double[]</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(double[] lhs, double[] rhs) {
    if (isEquals == false) {
      return this;
    }
    if (lhs == rhs) {
      return this;
    }
    if (lhs == null || rhs == null) {
      this.setEquals(false);
      return this;
    }
    if (lhs.length != rhs.length) {
      this.setEquals(false);
      return this;
    }
    for (int i = 0; i < lhs.length && isEquals; ++i) {
      append(lhs[i], rhs[i]);
    }
    return this;
  }

  /**
   * <p>
   * Deep comparison of array of <code>float</code>. Length and all values are compared.
   * </p>
   * <p>
   * <p>
   * The method {@link #append(float, float)} is used.
   * </p>
   *
   * @param lhs the left hand <code>float[]</code>
   * @param rhs the right hand <code>float[]</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(float[] lhs, float[] rhs) {
    if (isEquals == false) {
      return this;
    }
    if (lhs == rhs) {
      return this;
    }
    if (lhs == null || rhs == null) {
      this.setEquals(false);
      return this;
    }
    if (lhs.length != rhs.length) {
      this.setEquals(false);
      return this;
    }
    for (int i = 0; i < lhs.length && isEquals; ++i) {
      append(lhs[i], rhs[i]);
    }
    return this;
  }

  /**
   * <p>
   * Deep comparison of array of <code>boolean</code>. Length and all values are compared.
   * </p>
   * <p>
   * <p>
   * The method {@link #append(boolean, boolean)} is used.
   * </p>
   *
   * @param lhs the left hand <code>boolean[]</code>
   * @param rhs the right hand <code>boolean[]</code>
   * @return EqualsBuilder - used to chain calls.
   */
  public EqualsBuilder append(boolean[] lhs, boolean[] rhs) {
    if (isEquals == false) {
      return this;
    }
    if (lhs == rhs) {
      return this;
    }
    if (lhs == null || rhs == null) {
      this.setEquals(false);
      return this;
    }
    if (lhs.length != rhs.length) {
      this.setEquals(false);
      return this;
    }
    for (int i = 0; i < lhs.length && isEquals; ++i) {
      append(lhs[i], rhs[i]);
    }
    return this;
  }

  /**
   * <p>
   * Returns <code>true</code> if the fields that have been checked are all equal.
   * </p>
   *
   * @return boolean
   */
  public boolean isEquals() {
    return this.isEquals;
  }

  /**
   * <p>
   * Returns <code>true</code> if the fields that have been checked are all equal.
   * </p>
   *
   * @return <code>true</code> if all of the fields that have been checked are equal,
   * <code>false</code> otherwise.
   * @since 3.0
   */
  public Boolean build() {
    return isEquals();
  }

  /**
   * Sets the <code>isEquals</code> value.
   *
   * @param isEquals The value to set.
   * @since 2.1
   */
  protected void setEquals(boolean isEquals) {
    this.isEquals = isEquals;
  }

  /**
   * Reset the EqualsBuilder so you can use the same object again
   *
   * @since 2.5
   */
  public void reset() {
    this.isEquals = true;
  }
}