package org.succlz123.utils; import java.io.IOException; import java.io.Serializable; import java.lang.reflect.Array; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.Collection; import java.util.Comparator; import java.util.HashMap; /** * <p>Operations on {@code Object}.</p> * * <p>This class tries to handle {@code null} input gracefully. * An exception will generally not be thrown for a {@code null} input. * Each method documents its behaviour in more detail.</p> * * <p>#ThreadSafe#</p> * @since 1.0 * @version $Id: ObjectUtils.java 1199894 2011-11-09 17:53:59Z ggregory $ */ public class ObjectUtils { /** * <p>Singleton used as a {@code null} placeholder where * {@code null} has another meaning.</p> * * <p>For example, in a {@code HashMap} the * {@link HashMap#get(Object)} method returns * {@code null} if the {@code Map} contains {@code null} or if there * is no matching key. The {@code Null} placeholder can be used to * distinguish between these two cases.</p> * * <p>Another example is {@code Hashtable}, where {@code null} * cannot be stored.</p> * * <p>This instance is Serializable.</p> */ public static final Null NULL = new Null(); /** * <p>{@code ObjectUtils} instances should NOT be constructed in * standard programming. Instead, the static methods on the class should * be used, such as {@code ObjectUtils.defaultIfNull("a","b");}.</p> * * <p>This constructor is public to permit tools that require a JavaBean * instance to operate.</p> */ public ObjectUtils() { super(); } // Defaulting //----------------------------------------------------------------------- /** * <p>Returns a default value if the object passed is {@code null}.</p> * * <pre> * ObjectUtils.defaultIfNull(null, null) = null * ObjectUtils.defaultIfNull(null, "") = "" * ObjectUtils.defaultIfNull(null, "zz") = "zz" * ObjectUtils.defaultIfNull("abc", *) = "abc" * ObjectUtils.defaultIfNull(Boolean.TRUE, *) = Boolean.TRUE * </pre> * * @param <T> the type of the object * @param object the {@code Object} to test, may be {@code null} * @param defaultValue the default value to return, may be {@code null} * @return {@code object} if it is not {@code null}, defaultValue otherwise */ public static <T> T defaultIfNull(T object, T defaultValue) { return object != null ? object : defaultValue; } /** * <p>Returns the first value in the array which is not {@code null}. * If all the values are {@code null} or the array is {@code null} * or empty then {@code null} is returned.</p> * * <pre> * ObjectUtils.firstNonNull(null, null) = null * ObjectUtils.firstNonNull(null, "") = "" * ObjectUtils.firstNonNull(null, null, "") = "" * ObjectUtils.firstNonNull(null, "zz") = "zz" * ObjectUtils.firstNonNull("abc", *) = "abc" * ObjectUtils.firstNonNull(null, "xyz", *) = "xyz" * ObjectUtils.firstNonNull(Boolean.TRUE, *) = Boolean.TRUE * ObjectUtils.firstNonNull() = null * </pre> * * @param <T> the component type of the array * @param values the values to test, may be {@code null} or empty * @return the first value from {@code values} which is not {@code null}, * or {@code null} if there are no non-null values */ public static <T> T firstNonNull(T... values) { if (values != null) { for (T val : values) { if (val != null) { return val; } } } return null; } /** * <p>Returns the first value in the Collection which is not {@code null}. * If all the values are {@code null} or the array is {@code null} * or empty then {@code null} is returned.</p> * * <pre> * ObjectUtils.firstNonNull([null, null]) = null * ObjectUtils.firstNonNull([null, ""]) = "" * ObjectUtils.firstNonNull([null, null, ""]) = "" * ObjectUtils.firstNonNull([null, "zz"]) = "zz" * ObjectUtils.firstNonNull(["abc", *]) = "abc" * ObjectUtils.firstNonNull([null, "xyz", *]) = "xyz" * ObjectUtils.firstNonNull([Boolean.TRUE, *]) = Boolean.TRUE * </pre> * * @param <T> the component type of the array * @param values the values to test, may be {@code null} or empty * @return the first value from {@code values} which is not {@code null}, * or {@code null} if there are no non-null values */ public static <T> T firstNonNull(Collection<T> values) { if (values != null) { for (T val : values) { if (val != null) { return val; } } } return null; } // Null-safe equals/hashCode //----------------------------------------------------------------------- /** * <p>Compares two objects for equality, where either one or both * objects may be {@code null}.</p> * * <pre> * ObjectUtils.equals(null, null) = true * ObjectUtils.equals(null, "") = false * ObjectUtils.equals("", null) = false * ObjectUtils.equals("", "") = true * ObjectUtils.equals(Boolean.TRUE, null) = false * ObjectUtils.equals(Boolean.TRUE, "true") = false * ObjectUtils.equals(Boolean.TRUE, Boolean.TRUE) = true * ObjectUtils.equals(Boolean.TRUE, Boolean.FALSE) = false * </pre> * * @param object1 the first object, may be {@code null} * @param object2 the second object, may be {@code null} * @return {@code true} if the values of both objects are the same */ public static boolean equals(Object object1, Object object2) { if (object1 == object2) { return true; } if (object1 == null || object2 == null) { return false; } return object1.equals(object2); } /** * <p>Gets the hash code of an object returning zero when the * object is {@code null}.</p> * * <pre> * ObjectUtils.hashCode(null) = 0 * ObjectUtils.hashCode(obj) = obj.hashCode() * </pre> * * @param obj the object to obtain the hash code of, may be {@code null} * @return the hash code of the object, or zero if null */ public static int hashCode(Object obj) { // hashCode(Object) retained for performance, as hash code is often critical return obj == null ? 0 : obj.hashCode(); } // Identity ToString //----------------------------------------------------------------------- /** * <p>Gets the toString that would be produced by {@code Object} * if a class did not override toString itself. {@code null} * will return {@code null}.</p> * * <pre> * ObjectUtils.identityToString(null) = null * ObjectUtils.identityToString("") = "java.lang.String@1e23" * ObjectUtils.identityToString(Boolean.TRUE) = "java.lang.Boolean@7fa" * </pre> * * @param object the object to create a toString for, may be * {@code null} * @return the default toString text, or {@code null} if * {@code null} passed in */ public static String identityToString(Object object) { if (object == null) { return null; } StringBuffer buffer = new StringBuffer(); identityToString(buffer, object); return buffer.toString(); } /** * <p>Appends the toString that would be produced by {@code Object} * if a class did not override toString itself. {@code null} * will throw a NullPointerException for either of the two parameters. </p> * <p/> * <pre> * ObjectUtils.identityToString(appendable, "") = appendable.append("java.lang.String@1e23" * ObjectUtils.identityToString(appendable, Boolean.TRUE) = appendable.append("java.lang.Boolean@7fa" * ObjectUtils.identityToString(appendable, Boolean.TRUE) = appendable.append("java.lang.Boolean@7fa") * </pre> * * @param appendable the appendable to append to * @param object the object to create a toString for * @throws IOException if an I/O error occurs */ public static void identityToString(final Appendable appendable, final Object object) throws IOException { if (object == null) { throw new NullPointerException("Cannot get the toString of a null identity"); } appendable.append(object.getClass().getName()) .append('@') .append(Integer.toHexString(System.identityHashCode(object))); } /** * <p>Appends the toString that would be produced by {@code Object} * if a class did not override toString itself. {@code null} * will throw a NullPointerException for either of the two parameters. </p> * * <pre> * ObjectUtils.identityToString(buf, "") = buf.append("java.lang.String@1e23" * ObjectUtils.identityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa" * ObjectUtils.identityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa") * </pre> * * @param buffer the buffer to append to * @param object the object to create a toString for */ public static void identityToString(StringBuffer buffer, Object object) { if (object == null) { throw new NullPointerException("Cannot get the toString of a null identity"); } buffer.append(object.getClass().getName()) .append('@') .append(Integer.toHexString(System.identityHashCode(object))); } // ToString //----------------------------------------------------------------------- /** * <p>Gets the {@code toString} of an {@code Object} returning * an empty string ("") if {@code null} input.</p> * * <pre> * ObjectUtils.toString(null) = "" * ObjectUtils.toString("") = "" * ObjectUtils.toString("bat") = "bat" * ObjectUtils.toString(Boolean.TRUE) = "true" * </pre> * * @see String#valueOf(Object) * @param obj the Object to {@code toString}, may be null * @return the passed in Object's toString, or nullStr if {@code null} input */ public static String toString(Object obj) { return obj == null ? "" : obj.toString(); } /** * <p>Gets the {@code toString} of an {@code Object} returning * a specified text if {@code null} input.</p> * * <pre> * ObjectUtils.toString(null, null) = null * ObjectUtils.toString(null, "null") = "null" * ObjectUtils.toString("", "null") = "" * ObjectUtils.toString("bat", "null") = "bat" * ObjectUtils.toString(Boolean.TRUE, "null") = "true" * </pre> * * @see String#valueOf(Object) * @param obj the Object to {@code toString}, may be null * @param nullStr the String to return if {@code null} input, may be null * @return the passed in Object's toString, or nullStr if {@code null} input * @since 1.0 */ public static String toString(Object obj, String nullStr) { return obj == null ? nullStr : obj.toString(); } // Comparable //----------------------------------------------------------------------- /** * <p>Null safe comparison of Comparables.</p> * * @param <T> type of the values processed by this method * @param values the set of comparable values, may be null * @return * <ul> * <li>If any objects are non-null and unequal, the lesser object. * <li>If all objects are non-null and equal, the first. * <li>If any of the comparables are null, the lesser of the non-null objects. * <li>If all the comparables are null, null is returned. * </ul> */ public static <T extends Comparable<? super T>> T min(T... values) { T result = null; if (values != null) { for (T value : values) { if (compare(value, result, true) < 0) { result = value; } } } return result; } /** * <p>Null safe comparison of Comparables.</p> * * @param <T> type of the values processed by this method * @param values the set of comparable values, may be null * @return * <ul> * <li>If any objects are non-null and unequal, the greater object. * <li>If all objects are non-null and equal, the first. * <li>If any of the comparables are null, the greater of the non-null objects. * <li>If all the comparables are null, null is returned. * </ul> */ public static <T extends Comparable<? super T>> T max(T... values) { T result = null; if (values != null) { for (T value : values) { if (compare(value, result, false) > 0) { result = value; } } } return result; } /** * <p>Null safe comparison of Comparables. * {@code null} is assumed to be less than a non-{@code null} value.</p> * * @param <T> type of the values processed by this method * @param c1 the first comparable, may be null * @param c2 the second comparable, may be null * @return a negative value if c1 < c2, zero if c1 = c2 * and a positive value if c1 > c2 */ public static <T extends Comparable<? super T>> int compare(T c1, T c2) { return compare(c1, c2, false); } /** * <p>Null safe comparison of Comparables.</p> * * @param <T> type of the values processed by this method * @param c1 the first comparable, may be null * @param c2 the second comparable, may be null * @param nullGreater if true {@code null} is considered greater * than a non-{@code null} value or if false {@code null} is * considered less than a Non-{@code null} value * @return a negative value if c1 < c2, zero if c1 = c2 * and a positive value if c1 > c2 * @see Comparator#compare(Object, Object) */ public static <T extends Comparable<? super T>> int compare(T c1, T c2, boolean nullGreater) { if (c1 == c2) { return 0; } else if (c1 == null) { return nullGreater ? 1 : -1; } else if (c2 == null) { return nullGreater ? -1 : 1; } return c1.compareTo(c2); } // cloning //----------------------------------------------------------------------- /** * <p>Clone an object.</p> * * @param <T> the type of the object * @param obj the object to clone, null returns null * @return the clone if the object implements {@link Cloneable} otherwise {@code null} * @throws CloneFailedException if the object is cloneable and the clone operation fails */ public static <T> T clone(final T obj) { if (obj instanceof Cloneable) { final Object result; if (obj.getClass().isArray()) { final Class<?> componentType = obj.getClass().getComponentType(); if (!componentType.isPrimitive()) { result = ((Object[]) obj).clone(); } else { int length = Array.getLength(obj); result = Array.newInstance(componentType, length); System.arraycopy(obj, 0, result, 0, length); } } else { try { final Method clone = obj.getClass().getMethod("clone"); result = clone.invoke(obj); } catch (final NoSuchMethodException e) { throw new CloneFailedException("Cloneable type " + obj.getClass().getName() + " has no clone method", e); } catch (final IllegalAccessException e) { throw new CloneFailedException("Cannot clone Cloneable type " + obj.getClass().getName(), e); } catch (final InvocationTargetException e) { throw new CloneFailedException("Exception cloning Cloneable type " + obj.getClass().getName(), e.getCause()); } } @SuppressWarnings("unchecked") final T checked = (T) result; return checked; } return null; } /** * <p>Clone an object if possible.</p> * * <p>This method is similar to {@link #clone(Object)}, but will return the provided * instance as the return value instead of {@code null} if the instance * is not cloneable. This is more convenient if the caller uses different * implementations (e.g. of a service) and some of the implementations do not allow concurrent * processing or have state. In such cases the implementation can simply provide a proper * clone implementation and the caller's code does not have to change.</p> * * @param <T> the type of the object * @param obj the object to clone, null returns null * @return the clone if the object implements {@link Cloneable} otherwise the object itself * @throws CloneFailedException if the object is cloneable and the clone operation fails */ public static <T> T cloneIfPossible(final T obj) { final T clone = clone(obj); return clone == null ? obj : clone; } // Null //----------------------------------------------------------------------- /** * <p>Class used as a null placeholder where {@code null} * has another meaning.</p> * * <p>For example, in a {@code HashMap} the * {@link HashMap#get(Object)} method returns * {@code null} if the {@code Map} contains {@code null} or if there is * no matching key. The {@code Null} placeholder can be used to distinguish * between these two cases.</p> * * <p>Another example is {@code Hashtable}, where {@code null} * cannot be stored.</p> */ public static class Null implements Serializable { /** * Required for serialization support. Declare serialization compatibility with Commons Lang 1.0 * * @see Serializable */ private static final long serialVersionUID = 7092611880189329093L; /** * Restricted constructor - singleton. */ Null() { super(); } /** * <p>Ensure singleton.</p> * * @return the singleton value */ private Object readResolve() { return ObjectUtils.NULL; } } }