Java example source code file (ClassUtils.java)

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Java - Java tags/keywords

class, classloader, classnotfoundexception, hashmap, inner_class_separator_char, iterable, iterator, list, map, object, override, reflection, set, string, stringbuilder, util

The ClassUtils.java Java example source code

/*
 * 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;

import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.commons.lang3.mutable.MutableObject;

/**
 * <p>Operates on classes without using reflection.

 *
 * <p>This class handles invalid {@code null} inputs as best it can.
 * Each method documents its behaviour in more detail.</p>
 *
 * <p>The notion of a {@code canonical name} includes the human
 * readable name for the type, for example {@code int[]}. The
 * non-canonical method variants work with the JVM names, such as
 * {@code [I}. </p>
 *
 * @since 2.0
 */
public class ClassUtils {
    /**
     * Inclusivity literals for {@link #hierarchy(Class, Interfaces)}.
     * @since 3.2
     */
    public enum Interfaces {
        INCLUDE, EXCLUDE
    }

    /**
     * The package separator character: <code>'.' == {@value}.
     */
    public static final char PACKAGE_SEPARATOR_CHAR = '.';

    /**
     * The package separator String: <code>".".
     */
    public static final String PACKAGE_SEPARATOR = String.valueOf(PACKAGE_SEPARATOR_CHAR);

    /**
     * The inner class separator character: <code>'$' == {@value}.
     */
    public static final char INNER_CLASS_SEPARATOR_CHAR = '$';

    /**
     * The inner class separator String: {@code "$"}.
     */
    public static final String INNER_CLASS_SEPARATOR = String.valueOf(INNER_CLASS_SEPARATOR_CHAR);

    /**
     * Maps primitive {@code Class}es to their corresponding wrapper {@code Class}.
     */
    private static final Map<Class> primitiveWrapperMap = new HashMap, Class>();
    static {
         primitiveWrapperMap.put(Boolean.TYPE, Boolean.class);
         primitiveWrapperMap.put(Byte.TYPE, Byte.class);
         primitiveWrapperMap.put(Character.TYPE, Character.class);
         primitiveWrapperMap.put(Short.TYPE, Short.class);
         primitiveWrapperMap.put(Integer.TYPE, Integer.class);
         primitiveWrapperMap.put(Long.TYPE, Long.class);
         primitiveWrapperMap.put(Double.TYPE, Double.class);
         primitiveWrapperMap.put(Float.TYPE, Float.class);
         primitiveWrapperMap.put(Void.TYPE, Void.TYPE);
    }

    /**
     * Maps wrapper {@code Class}es to their corresponding primitive types.
     */
    private static final Map<Class> wrapperPrimitiveMap = new HashMap, Class>();
    static {
        for (final Map.Entry<Class> entry : primitiveWrapperMap.entrySet()) {
            final Class<?> primitiveClass = entry.getKey();
            final Class<?> wrapperClass = entry.getValue();
            if (!primitiveClass.equals(wrapperClass)) {
                wrapperPrimitiveMap.put(wrapperClass, primitiveClass);
            }
        }
    }

    /**
     * Maps a primitive class name to its corresponding abbreviation used in array class names.
     */
    private static final Map<String, String> abbreviationMap;

    /**
     * Maps an abbreviation used in array class names to corresponding primitive class name.
     */
    private static final Map<String, String> reverseAbbreviationMap;

    /**
     * Feed abbreviation maps
     */
    static {
        final Map<String, String> m = new HashMap();
        m.put("int", "I");
        m.put("boolean", "Z");
        m.put("float", "F");
        m.put("long", "J");
        m.put("short", "S");
        m.put("byte", "B");
        m.put("double", "D");
        m.put("char", "C");
        m.put("void", "V");
        final Map<String, String> r = new HashMap();
        for (final Map.Entry<String, String> e : m.entrySet()) {
            r.put(e.getValue(), e.getKey());
        }
        abbreviationMap = Collections.unmodifiableMap(m);
        reverseAbbreviationMap = Collections.unmodifiableMap(r);
    }

    /**
     * <p>ClassUtils instances should NOT be constructed in standard programming.
     * Instead, the class should be used as
     * {@code ClassUtils.getShortClassName(cls)}.</p>
     *
     * <p>This constructor is public to permit tools that require a JavaBean
     * instance to operate.</p>
     */
    public ClassUtils() {
      super();
    }

    // Short class name
    // ----------------------------------------------------------------------
    /**
     * <p>Gets the class name minus the package name for an {@code Object}.

     *
     * @param object  the class to get the short name for, may be null
     * @param valueIfNull  the value to return if null
     * @return the class name of the object without the package name, or the null value
     */
    public static String getShortClassName(final Object object, final String valueIfNull) {
        if (object == null) {
            return valueIfNull;
        }
        return getShortClassName(object.getClass());
    }

    /**
     * <p>Gets the class name minus the package name from a {@code Class}.

     *
     * <p>Consider using the Java 5 API {@link Class#getSimpleName()} instead.
     * The one known difference is that this code will return {@code "Map.Entry"} while
     * the {@code java.lang.Class} variant will simply return {@code "Entry"}. </p>
     *
     * @param cls  the class to get the short name for.
     * @return the class name without the package name or an empty string
     */
    public static String getShortClassName(final Class<?> cls) {
        if (cls == null) {
            return StringUtils.EMPTY;
        }
        return getShortClassName(cls.getName());
    }

    /**
     * <p>Gets the class name minus the package name from a String.

     *
     * <p>The string passed in is assumed to be a class name - it is not checked.


     * <p>Note that this method differs from Class.getSimpleName() in that this will
     * return {@code "Map.Entry"} whilst the {@code java.lang.Class} variant will simply
     * return {@code "Entry"}. </p>
     *
     * @param className  the className to get the short name for
     * @return the class name of the class without the package name or an empty string
     */
    public static String getShortClassName(String className) {
        if (StringUtils.isEmpty(className)) {
            return StringUtils.EMPTY;
        }

        final StringBuilder arrayPrefix = new StringBuilder();

        // Handle array encoding
        if (className.startsWith("[")) {
            while (className.charAt(0) == '[') {
                className = className.substring(1);
                arrayPrefix.append("[]");
            }
            // Strip Object type encoding
            if (className.charAt(0) == 'L' && className.charAt(className.length() - 1) == ';') {
                className = className.substring(1, className.length() - 1);
            }

            if (reverseAbbreviationMap.containsKey(className)) {
                className = reverseAbbreviationMap.get(className);
            }
        }

        final int lastDotIdx = className.lastIndexOf(PACKAGE_SEPARATOR_CHAR);
        final int innerIdx = className.indexOf(
                INNER_CLASS_SEPARATOR_CHAR, lastDotIdx == -1 ? 0 : lastDotIdx + 1);
        String out = className.substring(lastDotIdx + 1);
        if (innerIdx != -1) {
            out = out.replace(INNER_CLASS_SEPARATOR_CHAR, PACKAGE_SEPARATOR_CHAR);
        }
        return out + arrayPrefix;
    }

    /**
     * <p>Null-safe version of aClass.getSimpleName()

     *
     * @param cls the class for which to get the simple name.
     * @return the simple class name.
     * @since 3.0
     * @see Class#getSimpleName()
     */
    public static String getSimpleName(final Class<?> cls) {
        if (cls == null) {
            return StringUtils.EMPTY;
        }
        return cls.getSimpleName();
    }

    /**
     * <p>Null-safe version of aClass.getSimpleName()

     *
     * @param object the object for which to get the simple class name.
     * @param valueIfNull the value to return if <code>object is null
     * @return the simple class name.
     * @since 3.0
     * @see Class#getSimpleName()
     */
    public static String getSimpleName(final Object object, final String valueIfNull) {
        if (object == null) {
            return valueIfNull;
        }
        return getSimpleName(object.getClass());
    }

    // Package name
    // ----------------------------------------------------------------------
    /**
     * <p>Gets the package name of an {@code Object}.

     *
     * @param object  the class to get the package name for, may be null
     * @param valueIfNull  the value to return if null
     * @return the package name of the object, or the null value
     */
    public static String getPackageName(final Object object, final String valueIfNull) {
        if (object == null) {
            return valueIfNull;
        }
        return getPackageName(object.getClass());
    }

    /**
     * <p>Gets the package name of a {@code Class}.

     *
     * @param cls  the class to get the package name for, may be {@code null}.
     * @return the package name or an empty string
     */
    public static String getPackageName(final Class<?> cls) {
        if (cls == null) {
            return StringUtils.EMPTY;
        }
        return getPackageName(cls.getName());
    }

    /**
     * <p>Gets the package name from a {@code String}.

     *
     * <p>The string passed in is assumed to be a class name - it is not checked.

     * <p>If the class is unpackaged, return an empty string.

     *
     * @param className  the className to get the package name for, may be {@code null}
     * @return the package name or an empty string
     */
    public static String getPackageName(String className) {
        if (StringUtils.isEmpty(className)) {
            return StringUtils.EMPTY;
        }

        // Strip array encoding
        while (className.charAt(0) == '[') {
            className = className.substring(1);
        }
        // Strip Object type encoding
        if (className.charAt(0) == 'L' && className.charAt(className.length() - 1) == ';') {
            className = className.substring(1);
        }

        final int i = className.lastIndexOf(PACKAGE_SEPARATOR_CHAR);
        if (i == -1) {
            return StringUtils.EMPTY;
        }
        return className.substring(0, i);
    }

    // Abbreviated name
    // ----------------------------------------------------------------------
    /**
     * <p>Gets the abbreviated name of a {@code Class}.

     *
     * @param cls  the class to get the abbreviated name for, may be {@code null}
     * @param len  the desired length of the abbreviated name
     * @return the abbreviated name or an empty string
     * @throws IllegalArgumentException if len <= 0
     * @see #getAbbreviatedName(String, int)
     * @since 3.4
     */
    public static String getAbbreviatedName(final Class<?> cls, int len) {
      if (cls == null) {
        return StringUtils.EMPTY;
      }
      return getAbbreviatedName(cls.getName(), len);
    }

    /**
     * <p>Gets the abbreviated class name from a {@code String}.

     *
     * <p>The string passed in is assumed to be a class name - it is not checked.

     *
     * <p>The abbreviation algorithm will shorten the class name, usually without
     * significant loss of meaning.</p>
     * <p>The abbreviated class name will always include the complete package hierarchy.
     * If enough space is available, rightmost sub-packages will be displayed in full
     * length.</p>
     *
     * <p>The following table illustrates the algorithm:

     * <table summary="abbreviation examples">
     * <tr>