equalsbuilder.java

Classifier4J是一个很好的基于java的分类器,里面有Native bayes和KNN等方法的文本分类.另外还 提供了分词和自动摘要等功能

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package net.sf.classifier4J.util;

import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;

/**
 * <p>Assists in implementing {@link Object#equals(Object)} methods.</p>
 *
 * <p>Originally from the Apache commons-lang package</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>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>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>Typical use for the code is as follows:</p>
 * <pre>
 * public boolean equals(Object o) {
 *   if ( !(o instanceof MyClass) ) {
 *    return false;
 *   }
 *  MyClass rhs = (MyClass) o;
 *  return new EqualsBuilder()
 *                 .appendSuper(super.equals(o))
 *                 .append(field1, rhs.field1)
 *                 .append(field2, rhs.field2)
 *                 .append(field3, rhs.field3)
 *                 .isEquals();
 *  }
 * </pre>
 *
 * <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> A typical invocation for this method would look like:</p>
 * <pre>
 * public boolean equals(Object o) {
 *   return EqualsBuilder.reflectionEquals(this, o);
 * }
 * </pre>
 *
 * @author <a href="mailto:[e-mail]">Steve Downey</a>
 * @author Stephen Colebourne
 * @author Gary Gregory
 * @author Pete Gieser
 * @since 1.0
 * @version $Id: EqualsBuilder.java,v 1.1 2005/02/04 05:30:28 nicklothian Exp $
 */
public class EqualsBuilder {
    /**
     * If the fields tested are equals.
     */
    private boolean isEquals;

    /**
     * <p>Constructor for EqualsBuilder.</p>
     *
     * <p>Starts off assuming that equals is <code>true</code>.</p>
     * @see java.lang.Object#equals
     */
    public EqualsBuilder() {
        super();
        isEquals = true;
    }

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

    /**
     * <p>This method uses reflection to determine if the two <code>Object</code>s
     * are equal.</p>
     *
     * <p>It uses <code>AccessibleObject.setAccessible</code> to gain access to private
     * fields. This means that it will throw a security exception if run under
     * a security manager, if the permissions are not set up correctly. It is also
     * not as efficient as testing explicitly.</p>
     *
     * <p>Transient members will be not be tested, as they are likely derived
     * fields, and not part of the value of the Object.</p>
     *
     * <p>Static fields will not be tested. Superclass fields will be included.</p>
     *
     * @param lhs  <code>this</code> object
     * @param rhs  the other object
     * @return <code>true</code> if the two Objects have tested equals.
     */
    public static boolean reflectionEquals(Object lhs, Object rhs) {
        return reflectionEquals(lhs, rhs, false, null);
    }

    /**
     * <p>This method uses reflection to determine if the two <code>Object</code>s
     * are equal.</p>
     *
     * <p>It uses <code>AccessibleObject.setAccessible</code> to gain access to private
     * fields. This means that it will throw a security exception if run under
     * a security manager, if the permissions are not set up correctly. It is also
     * not as efficient as testing explicitly.</p>
     *
     * <p>If the TestTransients parameter is set to <code>true</code>, transient
     * members will be tested, otherwise they are ignored, as they are likely
     * derived fields, and not part of the value of the <code>Object</code>.</p>
     *
     * <p>Static fields will not be tested. Superclass fields will be included.</p>
     *
     * @param lhs  <code>this</code> object
     * @param rhs  the other object
     * @param testTransients  whether to include transient fields
     * @return <code>true</code> if the two Objects have tested equals.
     */
    public static boolean reflectionEquals(Object lhs, Object rhs, boolean testTransients) {
        return reflectionEquals(lhs, rhs, testTransients, null);
    }

    /**
     * <p>This method uses reflection to determine if the two <code>Object</code>s
     * are equal.</p>
     *
     * <p>It uses <code>AccessibleObject.setAccessible</code> to gain access to private
     * fields. This means that it will throw a security exception if run under
     * a security manager, if the permissions are not set up correctly. It is also
     * not as efficient as testing explicitly.</p>
     *
     * <p>If the testTransients parameter is set to <code>true</code>, transient
     * members will be tested, otherwise they are ignored, as they are likely
     * derived fields, and not part of the value of the <code>Object</code>.</p>
     *
     * <p>Static fields will not be included. Superclass fields will be appended
     * up to and including the specified superclass. A null superclass is treated
     * as java.lang.Object.</p>
     *
     * @param lhs  <code>this</code> object
     * @param rhs  the other object
     * @param testTransients  whether to include transient fields
     * @param reflectUpToClass  the superclass to reflect up to (inclusive),
     *  may be <code>null</code>
     * @return <code>true</code> if the two Objects have tested equals.
     * @since 2.0
     */
    public static boolean reflectionEquals(Object lhs, Object rhs, boolean testTransients, Class reflectUpToClass) {
        if (lhs == rhs) {
            return true;
        }
        if (lhs == null || rhs == null) {
            return false;
        }
        // Find the leaf class since there may be transients in the leaf 
        // class or in classes between the leaf and root.
        // If we are not testing transients or a subclass has no ivars, 
        // then a subclass can test equals to a superclass.
        Class lhsClass = lhs.getClass();
        Class rhsClass = rhs.getClass();
        Class testClass;
        if (lhsClass.isInstance(rhs)) {
            testClass = lhsClass;
            if (!rhsClass.isInstance(lhs)) {
                // rhsClass is a subclass of lhsClass
                testClass = rhsClass;
            }
        } else if (rhsClass.isInstance(lhs)) {
            testClass = rhsClass;
            if (!lhsClass.isInstance(rhs)) {
                // lhsClass is a subclass of rhsClass
                testClass = lhsClass;
            }
        } else {
            // The two classes are not related.
            return false;
        }
        EqualsBuilder equalsBuilder = new EqualsBuilder();
        try {
            reflectionAppend(lhs, rhs, testClass, equalsBuilder, testTransients);
            while (testClass.getSuperclass() != null && testClass != reflectUpToClass) {
                testClass = testClass.getSuperclass();
                reflectionAppend(lhs, rhs, testClass, equalsBuilder, testTransients);
            }
        } catch (IllegalArgumentException e) {
            // In this case, we tried to test a subclass vs. a superclass and
            // the subclass has ivars or the ivars are transient and 
            // we are testing transients.
            // If a subclass has ivars that we are trying to test them, we get an
            // exception and we know that the objects are not equal.
            return false;
        }
        return equalsBuilder.isEquals();
    }

    /**
     * <p>Appends the fields and values defined by the given object of the
     * given Class.</p>
     * 
     * @param lhs  the left hand object
     * @param rhs  the right hand object
     * @param clazz  the class to append details of
     * @param builder  the builder to append to
     * @param useTransients  whether to test transient fields
     */
    private static void reflectionAppend(
        Object lhs,
        Object rhs,
        Class clazz,
        EqualsBuilder builder,
        boolean useTransients) {
        Field[] fields = clazz.getDeclaredFields();
        AccessibleObject.setAccessible(fields, true);
        for (int i = 0; i < fields.length && builder.isEquals; i++) {
            Field f = fields[i];
            if ((f.getName().indexOf('$') == -1)
                && (useTransients || !Modifier.isTransient(f.getModifiers()))
                && (!Modifier.isStatic(f.getModifiers()))) {
                try {
                    builder.append(f.get(lhs), f.get(rhs));
                } catch (IllegalAccessException e) {
                    //this can't happen. Would get a Security exception instead
                    //throw a runtime exception in case the impossible happens.
                    throw new InternalError("Unexpected IllegalAccessException");
                }
            }
        }
    }

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

    /**
     * <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) {
            isEquals = 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 {
            //'Switch' on type of array, to dispatch to the correct handler
            // This handles multi dimensional arrays
            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>