Java tutorial
/* * Copyright 2002-2007 the original author or authors. * * 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 cn.remex.core.util; import java.lang.reflect.Array; import java.util.Arrays; /** * ? * Miscellaneous object utility methods. Mainly for internal use within the * framework; consider Jakarta's Commons Lang for a more comprehensive suite * of object utilities. * * @author Juergen Hoeller * @author Keith Donald * @author Rod Johnson * @author Rob Harrop * @author Alex Ruiz * @since 19.03.2004 * @see org.apache.commons.lang.ObjectUtils */ public abstract class ObjectUtils { private static final String ARRAY_ELEMENT_SEPARATOR = ", "; private static final String ARRAY_END = "}"; private static final String ARRAY_START = "{"; private static final String EMPTY_ARRAY = ARRAY_START + ARRAY_END; private static final String EMPTY_STRING = ""; private static final int INITIAL_HASH = 7; private static final int MULTIPLIER = 31; private static final String NULL_STRING = "null"; /** * Append the given Object to the given array, returning a new array * consisting of the input array contents plus the given Object. * @param array the array to append to (can be <code>null</code>) * @param obj the Object to append * @return the new array (of the same component type; never <code>null</code>) */ public static Object[] addObjectToArray(final Object[] array, final Object obj) { Class<?> compType = Object.class; if (array != null) { compType = array.getClass().getComponentType(); } else if (obj != null) { compType = obj.getClass(); } int newArrLength = array != null ? array.length + 1 : 1; Object[] newArr = (Object[]) Array.newInstance(compType, newArrLength); if (array != null) { System.arraycopy(array, 0, newArr, 0, array.length); } newArr[newArr.length - 1] = obj; return newArr; } /** * Check whether the given array contains the given element. * @param array the array to check (may be <code>null</code>, * in which case the return value will always be <code>false</code>) * @param element the element to check for * @return whether the element has been found in the given array */ public static boolean containsElement(final Object[] array, final Object element) { if (array == null) { return false; } for (Object element2 : array) { if (nullSafeEquals(element2, element)) { return true; } } return false; } /** * Return a content-based String representation if <code>obj</code> is * not <code>null</code>; otherwise returns an empty String. * <p>Differs from {@link #nullSafeToString(Object)} in that it returns * an empty String rather than "null" for a <code>null</code> value. * @param obj the object to build a display String for * @return a display String representation of <code>obj</code> * @see #nullSafeToString(Object) */ public static String getDisplayString(final Object obj) { if (obj == null) { return EMPTY_STRING; } return nullSafeToString(obj); } /** * Return a hex String form of an object's identity hash code. * @param obj the object * @return the object's identity code in hex notation */ public static String getIdentityHexString(final Object obj) { return Integer.toHexString(System.identityHashCode(obj)); } /** * Return the same value as <code>{@link Boolean#hashCode()}</code>. * @see Boolean#hashCode() */ public static int hashCode(final boolean bool) { return bool ? 1231 : 1237; } /** * Return the same value as <code>{@link Double#hashCode()}</code>. * @see Double#hashCode() */ public static int hashCode(final double dbl) { long bits = Double.doubleToLongBits(dbl); return hashCode(bits); } //--------------------------------------------------------------------- // Convenience methods for content-based equality/hash-code handling //--------------------------------------------------------------------- /** * Return the same value as <code>{@link Float#hashCode()}</code>. * @see Float#hashCode() */ public static int hashCode(final float flt) { return Float.floatToIntBits(flt); } /** * Return the same value as <code>{@link Long#hashCode()}</code>. * @see Long#hashCode() */ public static int hashCode(final long lng) { return (int) (lng ^ lng >>> 32); } /** * Return a String representation of an object's overall identity. * @param obj the object (may be <code>null</code>) * @return the object's identity as String representation, * or an empty String if the object was <code>null</code> */ public static String identityToString(final Object obj) { if (obj == null) { return EMPTY_STRING; } return obj.getClass().getName() + "@" + getIdentityHexString(obj); } /** * Return whether the given throwable is a checked exception: * that is, neither a RuntimeException nor an Error. * @param ex the throwable to check * @return whether the throwable is a checked exception * @see java.lang.Exception * @see java.lang.RuntimeException * @see java.lang.Error */ public static boolean isCheckedException(final Throwable ex) { return !(ex instanceof RuntimeException || ex instanceof Error); } /** * Check whether the given exception is compatible with the exceptions * declared in a throws clause. * @param ex the exception to checked * @param declaredExceptions the exceptions declared in the throws clause * @return whether the given exception is compatible */ public static boolean isCompatibleWithThrowsClause(final Throwable ex, final Class<?>[] declaredExceptions) { if (!isCheckedException(ex)) { return true; } if (declaredExceptions != null) { for (Class<?> declaredException : declaredExceptions) { if (declaredException.isAssignableFrom(ex.getClass())) { return true; } } } return false; } /** * Return whether the given array is empty: that is, <code>null</code> * or of zero length. * @param array the array to check * @return whether the given array is empty */ public static boolean isEmpty(final Object[] array) { return array == null || array.length == 0; } /** * Determine the class name for the given object. * <p>Returns <code>"null"</code> if <code>obj</code> is <code>null</code>. * @param obj the object to introspect (may be <code>null</code>) * @return the corresponding class name */ public static String nullSafeClassName(final Object obj) { return obj != null ? obj.getClass().getName() : NULL_STRING; } /** * Determine if the given objects are equal, returning <code>true</code> * if both are <code>null</code> or <code>false</code> if only one is * <code>null</code>. * <p>Compares arrays with <code>Arrays.equals</code>, performing an equality * check based on the array elements rather than the array reference. * @param o1 first Object to compare * @param o2 second Object to compare * @return whether the given objects are equal * @see java.util.Arrays#equals */ public static boolean nullSafeEquals(final Object o1, final Object o2) { if (o1 == o2) { return true; } if (o1 == null || o2 == null) { return false; } if (o1.equals(o2)) { return true; } if (o1.getClass().isArray() && o2.getClass().isArray()) { if (o1 instanceof Object[] && o2 instanceof Object[]) { return Arrays.equals((Object[]) o1, (Object[]) o2); } if (o1 instanceof boolean[] && o2 instanceof boolean[]) { return Arrays.equals((boolean[]) o1, (boolean[]) o2); } if (o1 instanceof byte[] && o2 instanceof byte[]) { return Arrays.equals((byte[]) o1, (byte[]) o2); } if (o1 instanceof char[] && o2 instanceof char[]) { return Arrays.equals((char[]) o1, (char[]) o2); } if (o1 instanceof double[] && o2 instanceof double[]) { return Arrays.equals((double[]) o1, (double[]) o2); } if (o1 instanceof float[] && o2 instanceof float[]) { return Arrays.equals((float[]) o1, (float[]) o2); } if (o1 instanceof int[] && o2 instanceof int[]) { return Arrays.equals((int[]) o1, (int[]) o2); } if (o1 instanceof long[] && o2 instanceof long[]) { return Arrays.equals((long[]) o1, (long[]) o2); } if (o1 instanceof short[] && o2 instanceof short[]) { return Arrays.equals((short[]) o1, (short[]) o2); } } return false; } /** * Return a hash code based on the contents of the specified array. * If <code>array</code> is <code>null</code>, this method returns 0. */ public static int nullSafeHashCode(final boolean[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + hashCode(array[i]); } return hash; } /** * Return a hash code based on the contents of the specified array. * If <code>array</code> is <code>null</code>, this method returns 0. */ public static int nullSafeHashCode(final byte[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + array[i]; } return hash; } /** * Return a hash code based on the contents of the specified array. * If <code>array</code> is <code>null</code>, this method returns 0. */ public static int nullSafeHashCode(final char[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + array[i]; } return hash; } /** * Return a hash code based on the contents of the specified array. * If <code>array</code> is <code>null</code>, this method returns 0. */ public static int nullSafeHashCode(final double[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + hashCode(array[i]); } return hash; } /** * Return a hash code based on the contents of the specified array. * If <code>array</code> is <code>null</code>, this method returns 0. */ public static int nullSafeHashCode(final float[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + hashCode(array[i]); } return hash; } /** * Return a hash code based on the contents of the specified array. * If <code>array</code> is <code>null</code>, this method returns 0. */ public static int nullSafeHashCode(final int[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + array[i]; } return hash; } /** * Return a hash code based on the contents of the specified array. * If <code>array</code> is <code>null</code>, this method returns 0. */ public static int nullSafeHashCode(final long[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + hashCode(array[i]); } return hash; } //--------------------------------------------------------------------- // Convenience methods for toString output //--------------------------------------------------------------------- /** * Return as hash code for the given object; typically the value of * <code>{@link Object#hashCode()}</code>. If the object is an array, * this method will delegate to any of the <code>nullSafeHashCode</code> * methods for arrays in this class. If the object is <code>null</code>, * this method returns 0. * @see #nullSafeHashCode(Object[]) * @see #nullSafeHashCode(boolean[]) * @see #nullSafeHashCode(byte[]) * @see #nullSafeHashCode(char[]) * @see #nullSafeHashCode(double[]) * @see #nullSafeHashCode(float[]) * @see #nullSafeHashCode(int[]) * @see #nullSafeHashCode(long[]) * @see #nullSafeHashCode(short[]) */ public static int nullSafeHashCode(final Object obj) { if (obj == null) { return 0; } if (obj.getClass().isArray()) { if (obj instanceof Object[]) { return nullSafeHashCode((Object[]) obj); } if (obj instanceof boolean[]) { return nullSafeHashCode((boolean[]) obj); } if (obj instanceof byte[]) { return nullSafeHashCode((byte[]) obj); } if (obj instanceof char[]) { return nullSafeHashCode((char[]) obj); } if (obj instanceof double[]) { return nullSafeHashCode((double[]) obj); } if (obj instanceof float[]) { return nullSafeHashCode((float[]) obj); } if (obj instanceof int[]) { return nullSafeHashCode((int[]) obj); } if (obj instanceof long[]) { return nullSafeHashCode((long[]) obj); } if (obj instanceof short[]) { return nullSafeHashCode((short[]) obj); } } return obj.hashCode(); } /** * Return a hash code based on the contents of the specified array. * If <code>array</code> is <code>null</code>, this method returns 0. */ public static int nullSafeHashCode(final Object[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + nullSafeHashCode(array[i]); } return hash; } /** * Return a hash code based on the contents of the specified array. * If <code>array</code> is <code>null</code>, this method returns 0. */ public static int nullSafeHashCode(final short[] array) { if (array == null) { return 0; } int hash = INITIAL_HASH; int arraySize = array.length; for (int i = 0; i < arraySize; i++) { hash = MULTIPLIER * hash + array[i]; } return hash; } /** * Return a String representation of the contents of the specified array. * <p>The String representation consists of a list of the array's elements, * enclosed in curly braces (<code>"{}"</code>). Adjacent elements are separated * by the characters <code>", "</code> (a comma followed by a space). Returns * <code>"null"</code> if <code>array</code> is <code>null</code>. * @param array the array to build a String representation for * @return a String representation of <code>array</code> */ public static String nullSafeToString(final boolean[] array) { if (array == null) { return NULL_STRING; } int length = array.length; if (length == 0) { return EMPTY_ARRAY; } StringBuffer buffer = new StringBuffer(); for (int i = 0; i < length; i++) { if (i == 0) { buffer.append(ARRAY_START); } else { buffer.append(ARRAY_ELEMENT_SEPARATOR); } buffer.append(array[i]); } buffer.append(ARRAY_END); return buffer.toString(); } /** * Return a String representation of the contents of the specified array. * <p>The String representation consists of a list of the array's elements, * enclosed in curly braces (<code>"{}"</code>). Adjacent elements are separated * by the characters <code>", "</code> (a comma followed by a space). Returns * <code>"null"</code> if <code>array</code> is <code>null</code>. * @param array the array to build a String representation for * @return a String representation of <code>array</code> */ public static String nullSafeToString(final byte[] array) { if (array == null) { return NULL_STRING; } int length = array.length; if (length == 0) { return EMPTY_ARRAY; } StringBuffer buffer = new StringBuffer(); for (int i = 0; i < length; i++) { if (i == 0) { buffer.append(ARRAY_START); } else { buffer.append(ARRAY_ELEMENT_SEPARATOR); } buffer.append(array[i]); } buffer.append(ARRAY_END); return buffer.toString(); } /** * Return a String representation of the contents of the specified array. * <p>The String representation consists of a list of the array's elements, * enclosed in curly braces (<code>"{}"</code>). Adjacent elements are separated * by the characters <code>", "</code> (a comma followed by a space). Returns * <code>"null"</code> if <code>array</code> is <code>null</code>. * @param array the array to build a String representation for * @return a String representation of <code>array</code> */ public static String nullSafeToString(final char[] array) { if (array == null) { return NULL_STRING; } int length = array.length; if (length == 0) { return EMPTY_ARRAY; } StringBuffer buffer = new StringBuffer(); for (int i = 0; i < length; i++) { if (i == 0) { buffer.append(ARRAY_START); } else { buffer.append(ARRAY_ELEMENT_SEPARATOR); } buffer.append("'").append(array[i]).append("'"); } buffer.append(ARRAY_END); return buffer.toString(); } /** * Return a String representation of the contents of the specified array. * <p>The String representation consists of a list of the array's elements, * enclosed in curly braces (<code>"{}"</code>). Adjacent elements are separated * by the characters <code>", "</code> (a comma followed by a space). Returns * <code>"null"</code> if <code>array</code> is <code>null</code>. * @param array the array to build a String representation for * @return a String representation of <code>array</code> */ public static String nullSafeToString(final double[] array) { if (array == null) { return NULL_STRING; } int length = array.length; if (length == 0) { return EMPTY_ARRAY; } StringBuffer buffer = new StringBuffer(); for (int i = 0; i < length; i++) { if (i == 0) { buffer.append(ARRAY_START); } else { buffer.append(ARRAY_ELEMENT_SEPARATOR); } buffer.append(array[i]); } buffer.append(ARRAY_END); return buffer.toString(); } /** * Return a String representation of the contents of the specified array. * <p>The String representation consists of a list of the array's elements, * enclosed in curly braces (<code>"{}"</code>). Adjacent elements are separated * by the characters <code>", "</code> (a comma followed by a space). Returns * <code>"null"</code> if <code>array</code> is <code>null</code>. * @param array the array to build a String representation for * @return a String representation of <code>array</code> */ public static String nullSafeToString(final float[] array) { if (array == null) { return NULL_STRING; } int length = array.length; if (length == 0) { return EMPTY_ARRAY; } StringBuffer buffer = new StringBuffer(); for (int i = 0; i < length; i++) { if (i == 0) { buffer.append(ARRAY_START); } else { buffer.append(ARRAY_ELEMENT_SEPARATOR); } buffer.append(array[i]); } buffer.append(ARRAY_END); return buffer.toString(); } /** * Return a String representation of the contents of the specified array. * <p>The String representation consists of a list of the array's elements, * enclosed in curly braces (<code>"{}"</code>). Adjacent elements are separated * by the characters <code>", "</code> (a comma followed by a space). Returns * <code>"null"</code> if <code>array</code> is <code>null</code>. * @param array the array to build a String representation for * @return a String representation of <code>array</code> */ public static String nullSafeToString(final int[] array) { if (array == null) { return NULL_STRING; } int length = array.length; if (length == 0) { return EMPTY_ARRAY; } StringBuffer buffer = new StringBuffer(); for (int i = 0; i < length; i++) { if (i == 0) { buffer.append(ARRAY_START); } else { buffer.append(ARRAY_ELEMENT_SEPARATOR); } buffer.append(array[i]); } buffer.append(ARRAY_END); return buffer.toString(); } /** * Return a String representation of the contents of the specified array. * <p>The String representation consists of a list of the array's elements, * enclosed in curly braces (<code>"{}"</code>). Adjacent elements are separated * by the characters <code>", "</code> (a comma followed by a space). Returns * <code>"null"</code> if <code>array</code> is <code>null</code>. * @param array the array to build a String representation for * @return a String representation of <code>array</code> */ public static String nullSafeToString(final long[] array) { if (array == null) { return NULL_STRING; } int length = array.length; if (length == 0) { return EMPTY_ARRAY; } StringBuffer buffer = new StringBuffer(); for (int i = 0; i < length; i++) { if (i == 0) { buffer.append(ARRAY_START); } else { buffer.append(ARRAY_ELEMENT_SEPARATOR); } buffer.append(array[i]); } buffer.append(ARRAY_END); return buffer.toString(); } /** * Return a String representation of the specified Object. * <p>Builds a String representation of the contents in case of an array. * Returns <code>"null"</code> if <code>obj</code> is <code>null</code>. * @param obj the object to build a String representation for * @return a String representation of <code>obj</code> */ public static String nullSafeToString(final Object obj) { if (obj == null) { return NULL_STRING; } if (obj instanceof String) { return (String) obj; } if (obj instanceof Object[]) { return nullSafeToString((Object[]) obj); } if (obj instanceof boolean[]) { return nullSafeToString((boolean[]) obj); } if (obj instanceof byte[]) { return nullSafeToString((byte[]) obj); } if (obj instanceof char[]) { return nullSafeToString((char[]) obj); } if (obj instanceof double[]) { return nullSafeToString((double[]) obj); } if (obj instanceof float[]) { return nullSafeToString((float[]) obj); } if (obj instanceof int[]) { return nullSafeToString((int[]) obj); } if (obj instanceof long[]) { return nullSafeToString((long[]) obj); } if (obj instanceof short[]) { return nullSafeToString((short[]) obj); } String str = obj.toString(); return str != null ? str : EMPTY_STRING; } /** * Return a String representation of the contents of the specified array. * <p>The String representation consists of a list of the array's elements, * enclosed in curly braces (<code>"{}"</code>). Adjacent elements are separated * by the characters <code>", "</code> (a comma followed by a space). Returns * <code>"null"</code> if <code>array</code> is <code>null</code>. * @param array the array to build a String representation for * @return a String representation of <code>array</code> */ public static String nullSafeToString(final Object[] array) { if (array == null) { return NULL_STRING; } int length = array.length; if (length == 0) { return EMPTY_ARRAY; } StringBuffer buffer = new StringBuffer(); for (int i = 0; i < length; i++) { if (i == 0) { buffer.append(ARRAY_START); } else { buffer.append(ARRAY_ELEMENT_SEPARATOR); } buffer.append(String.valueOf(array[i])); } buffer.append(ARRAY_END); return buffer.toString(); } /** * Return a String representation of the contents of the specified array. * <p>The String representation consists of a list of the array's elements, * enclosed in curly braces (<code>"{}"</code>). Adjacent elements are separated * by the characters <code>", "</code> (a comma followed by a space). Returns * <code>"null"</code> if <code>array</code> is <code>null</code>. * @param array the array to build a String representation for * @return a String representation of <code>array</code> */ public static String nullSafeToString(final short[] array) { if (array == null) { return NULL_STRING; } int length = array.length; if (length == 0) { return EMPTY_ARRAY; } StringBuffer buffer = new StringBuffer(); for (int i = 0; i < length; i++) { if (i == 0) { buffer.append(ARRAY_START); } else { buffer.append(ARRAY_ELEMENT_SEPARATOR); } buffer.append(array[i]); } buffer.append(ARRAY_END); return buffer.toString(); } /** * Convert the given array (which may be a primitive array) to an * object array (if necessary of primitive wrapper objects). * <p>A <code>null</code> source value will be converted to an * empty Object array. * @param source the (potentially primitive) array * @return the corresponding object array (never <code>null</code>) * @throws IllegalArgumentException if the parameter is not an array */ public static Object[] toObjectArray(final Object source) { if (source instanceof Object[]) { return (Object[]) source; } if (source == null) { return new Object[0]; } if (!source.getClass().isArray()) { throw new IllegalArgumentException("Source is not an array: " + source); } int length = Array.getLength(source); if (length == 0) { return new Object[0]; } Class<?> wrapperType = Array.get(source, 0).getClass(); Object[] newArray = (Object[]) Array.newInstance(wrapperType, length); for (int i = 0; i < length; i++) { newArray[i] = Array.get(source, i); } return newArray; } }