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.jdto.util; import java.util.HashMap; import java.util.Iterator; import java.util.Map; import org.apache.commons.lang.ArrayUtils; /** * This class has been extracted from the ClassUtils provided on the Apache * Commons-Lang library, the methods present in this class were copied here so * the dependency with that library could be relaxed to a lower version. * * Please note that this class may be removed on the future. * * @author Juan Alberto Lopez Cavallotti */ public class ClassUtils { /** * Maps primitive * <code>Class</code>es to their corresponding wrapper * <code>Class</code>. */ private static final Map primitiveWrapperMap = new HashMap(); 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</code>es to their corresponding primitive types. */ private static final Map wrapperPrimitiveMap = new HashMap(); static { for (Iterator it = primitiveWrapperMap.keySet().iterator(); it.hasNext();) { Class primitiveClass = (Class) it.next(); Class wrapperClass = (Class) primitiveWrapperMap.get(primitiveClass); if (!primitiveClass.equals(wrapperClass)) { wrapperPrimitiveMap.put(wrapperClass, primitiveClass); } } } // Is assignable // ---------------------------------------------------------------------- /** * <p>Checks if an array of Classes can be assigned to another array of * Classes.</p> * * <p>This method calls {@link #isAssignable(Class, Class) isAssignable} for * each Class pair in the input arrays. It can be used to check if a set of * arguments (the first parameter) are suitably compatible with a set of * method parameter types (the second parameter).</p> * * <p>Unlike the {@link Class#isAssignableFrom(java.lang.Class)} method, * this method takes into account widenings of primitive classes and * <code>null</code>s.</p> * * <p>Primitive widenings allow an int to be assigned to a * <code>long</code>, * <code>float</code> or * <code>double</code>. This method returns the correct result for these * cases.</p> * * <p><code>Null</code> may be assigned to any reference type. This method * will return * <code>true</code> if * <code>null</code> is passed in and the toClass is non-primitive.</p> * * <p>Specifically, this method tests whether the type represented by the * specified * <code>Class</code> parameter can be converted to the type represented by * this * <code>Class</code> object via an identity conversion widening primitive * or widening reference conversion. See <em><a * href="http://java.sun.com/docs/books/jls/">The Java Language * Specification</a></em>, sections 5.1.1, 5.1.2 and 5.1.4 for details.</p> * * @param classArray the array of Classes to check, may be * <code>null</code> * @param toClassArray the array of Classes to try to assign into, may be * <code>null</code> * @return * <code>true</code> if assignment possible */ public static boolean isAssignable(Class[] classArray, Class[] toClassArray) { return isAssignable(classArray, toClassArray, false); } /** * <p>Checks if an array of Classes can be assigned to another array of * Classes.</p> * * <p>This method calls {@link #isAssignable(Class, Class) isAssignable} for * each Class pair in the input arrays. It can be used to check if a set of * arguments (the first parameter) are suitably compatible with a set of * method parameter types (the second parameter).</p> * * <p>Unlike the {@link Class#isAssignableFrom(java.lang.Class)} method, * this method takes into account widenings of primitive classes and * <code>null</code>s.</p> * * <p>Primitive widenings allow an int to be assigned to a * <code>long</code>, * <code>float</code> or * <code>double</code>. This method returns the correct result for these * cases.</p> * * <p><code>Null</code> may be assigned to any reference type. This method * will return * <code>true</code> if * <code>null</code> is passed in and the toClass is non-primitive.</p> * * <p>Specifically, this method tests whether the type represented by the * specified * <code>Class</code> parameter can be converted to the type represented by * this * <code>Class</code> object via an identity conversion widening primitive * or widening reference conversion. See <em><a * href="http://java.sun.com/docs/books/jls/">The Java Language * Specification</a></em>, sections 5.1.1, 5.1.2 and 5.1.4 for details.</p> * * @param classArray the array of Classes to check, may be * <code>null</code> * @param toClassArray the array of Classes to try to assign into, may be * <code>null</code> * @param autoboxing whether to use implicit autoboxing/unboxing between * primitives and wrappers * @return * <code>true</code> if assignment possible * @since 2.5 */ public static boolean isAssignable(Class[] classArray, Class[] toClassArray, boolean autoboxing) { if (ArrayUtils.isSameLength(classArray, toClassArray) == false) { return false; } if (classArray == null) { classArray = ArrayUtils.EMPTY_CLASS_ARRAY; } if (toClassArray == null) { toClassArray = ArrayUtils.EMPTY_CLASS_ARRAY; } for (int i = 0; i < classArray.length; i++) { if (isAssignable(classArray[i], toClassArray[i], autoboxing) == false) { return false; } } return true; } /** * <p>Checks if one * <code>Class</code> can be assigned to a variable of another * <code>Class</code>.</p> * * <p>Unlike the {@link Class#isAssignableFrom(java.lang.Class)} method, * this method takes into account widenings of primitive classes and * <code>null</code>s.</p> * * <p>Primitive widenings allow an int to be assigned to a long, float or * double. This method returns the correct result for these cases.</p> * * <p><code>Null</code> may be assigned to any reference type. This method * will return * <code>true</code> if * <code>null</code> is passed in and the toClass is non-primitive.</p> * * <p>Specifically, this method tests whether the type represented by the * specified * <code>Class</code> parameter can be converted to the type represented by * this * <code>Class</code> object via an identity conversion widening primitive * or widening reference conversion. See <em><a * href="http://java.sun.com/docs/books/jls/">The Java Language * Specification</a></em>, sections 5.1.1, 5.1.2 and 5.1.4 for details.</p> * * @param cls the Class to check, may be null * @param toClass the Class to try to assign into, returns false if null * @param autoboxing whether to use implicit autoboxing/unboxing between * primitives and wrappers * @return * <code>true</code> if assignment possible * @since 2.5 */ public static boolean isAssignable(Class cls, Class toClass, boolean autoboxing) { if (toClass == null) { return false; } // have to check for null, as isAssignableFrom doesn't if (cls == null) { return !(toClass.isPrimitive()); } //autoboxing: if (autoboxing) { if (cls.isPrimitive() && !toClass.isPrimitive()) { cls = primitiveToWrapper(cls); if (cls == null) { return false; } } if (toClass.isPrimitive() && !cls.isPrimitive()) { cls = wrapperToPrimitive(cls); if (cls == null) { return false; } } } if (cls.equals(toClass)) { return true; } if (cls.isPrimitive()) { if (toClass.isPrimitive() == false) { return false; } if (Integer.TYPE.equals(cls)) { return Long.TYPE.equals(toClass) || Float.TYPE.equals(toClass) || Double.TYPE.equals(toClass); } if (Long.TYPE.equals(cls)) { return Float.TYPE.equals(toClass) || Double.TYPE.equals(toClass); } if (Boolean.TYPE.equals(cls)) { return false; } if (Double.TYPE.equals(cls)) { return false; } if (Float.TYPE.equals(cls)) { return Double.TYPE.equals(toClass); } if (Character.TYPE.equals(cls)) { return Integer.TYPE.equals(toClass) || Long.TYPE.equals(toClass) || Float.TYPE.equals(toClass) || Double.TYPE.equals(toClass); } if (Short.TYPE.equals(cls)) { return Integer.TYPE.equals(toClass) || Long.TYPE.equals(toClass) || Float.TYPE.equals(toClass) || Double.TYPE.equals(toClass); } if (Byte.TYPE.equals(cls)) { return Short.TYPE.equals(toClass) || Integer.TYPE.equals(toClass) || Long.TYPE.equals(toClass) || Float.TYPE.equals(toClass) || Double.TYPE.equals(toClass); } // should never get here return false; } return toClass.isAssignableFrom(cls); } /** * <p>Converts the specified primitive Class object to its corresponding * wrapper Class object.</p> * * <p>NOTE: From v2.2, this method handles * <code>Void.TYPE</code>, returning * <code>Void.TYPE</code>.</p> * * @param cls the class to convert, may be null * @return the wrapper class for * <code>cls</code> or * <code>cls</code> if * <code>cls</code> is not a primitive. * <code>null</code> if null input. * @since 2.1 */ public static Class primitiveToWrapper(Class cls) { Class convertedClass = cls; if (cls != null && cls.isPrimitive()) { convertedClass = (Class) primitiveWrapperMap.get(cls); } return convertedClass; } /** * <p>Converts the specified wrapper class to its corresponding primitive * class.</p> * * <p>This method is the counter part of * <code>primitiveToWrapper()</code>. If the passed in class is a wrapper * class for a primitive type, this primitive type will be returned (e.g. * <code>Integer.TYPE</code> for * <code>Integer.class</code>). For other classes, or if the parameter is * <b>null</b>, the return value is <b>null</b>.</p> * * @param cls the class to convert, may be <b>null</b> * @return the corresponding primitive type if * <code>cls</code> is a wrapper class, <b>null</b> otherwise * @see #primitiveToWrapper(Class) * @since 2.4 */ public static Class wrapperToPrimitive(Class cls) { return (Class) wrapperPrimitiveMap.get(cls); } }