de.unkrig.commons.lang.ObjectUtil Maven / Gradle / Ivy
/*
* de.unkrig.commons - A general-purpose Java class library
*
* Copyright (c) 2011, Arno Unkrig
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
* following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the
* following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
* following disclaimer in the documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
* THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
package de.unkrig.commons.lang;
import java.lang.reflect.Array;
import java.nio.charset.Charset;
import java.util.EnumSet;
import java.util.regex.Pattern;
import de.unkrig.commons.nullanalysis.NotNull;
import de.unkrig.commons.nullanalysis.Nullable;
/**
* Various {@code java.lang.Object}-related utility methods.
*/
public final
class ObjectUtil {
private static final Pattern WORD_SEPARATOR = Pattern.compile("[\\s,]+");
private ObjectUtil() {}
/**
* The often-needed "equal" method that handles {@code null} references.
*
* Redeemed by {@code java.util.Objects.equals(Object, Object)} which is available since Java 1.7.
*
*
* @return Both arguments are {@code null}, or are {@link CharSequence}s with equal contents, or are equal
*/
public static boolean
equals(@Nullable T o1, @Nullable T o2) {
if (o1 == null) return o2 == null;
if (o2 == null) return false;
if (o1 instanceof CharSequence && o2 instanceof CharSequence) {
return StringUtil.equals((CharSequence) o1, (CharSequence) o2);
}
return o1.equals(o2);
}
/**
* @return {@code Null} iff {@code o == null}, otherwise {@code o.hashCode()}
*/
public static int
hashCode(@Nullable Object o) { return o == null ? 0 : o.hashCode(); }
/**
* @return Returns {@code value.toString()} or the {@code defaultValue} iff {@code value == null}
*/
public static String
toString(@Nullable T value, String defaultValue) { return value != null ? value.toString() : defaultValue; }
/**
* @return lhs, or rhs iff {@code lhs == null}
*/
public static T
or(@Nullable T lhs, T rhs) { return lhs == null ? rhs : lhs; }
/**
* Converts a string to an object of the given targetType.
*
* For primitive targetTypes, the corresponding wrapper object is returned.
*
*
* Supports all primitive types (except {@code void}), their wrapper types, {@link String}, {@code char[]},
* {@link Charset}, {@link Class}, {@link Pattern}, enum types, and classes that have a single-string-parameter
* constructor.
*
*
* Supports (one-dimensional) arrays of these types, where the text is split into words at commas
* and/or whitespace, and each word converted to the component type.
*
*
* Does not support collections, including {@link EnumSet}s, because the element type cannot be determined
* through REFLECTION. Usage of an array is recommended as a workaround, as follows:
*
* {@code
*String s = "RED,GREEN";
*Color[] tmp = ObjectUtil.fromString(s, Color[].class);
*
*List list = Arrays.asList(tmp);
*EnumSet enumSet = EnumSet.copyOf(Arrays.asList(tmp));
*Set set = new HashSet(Arrays.asList(tmp));
*}
*
* @throws NumberFormatException The string could not be converted to the targetType
* @throws IllegalArgumentException The string could not be converted to the targetType
* @throws RuntimeException The string could not be converted to the targetType
*/
@SuppressWarnings("unchecked") public static T
fromString(String text, Class targetType) {
if (targetType.isArray()) {
Class componentType = targetType.getComponentType();
String[] words = ObjectUtil.WORD_SEPARATOR.split(text);
Object array = Array.newInstance(componentType, words.length);
for (int i = 0; i < words.length; i++) {
Array.set(array, i, ObjectUtil.fromString(words[i], componentType));
}
return (T) array;
}
if (targetType == String.class) return (T) text;
try {
if (targetType == boolean.class || targetType == Boolean.class) return (T) Boolean.valueOf(text);
if (targetType == byte.class || targetType == Byte.class) return (T) Byte.valueOf(text);
if (targetType == short.class || targetType == Short.class) return (T) Short.valueOf(text);
if (targetType == int.class || targetType == Integer.class) return (T) Integer.valueOf(text);
if (targetType == long.class || targetType == Long.class) return (T) Long.valueOf(text);
if (targetType == float.class || targetType == Float.class) return (T) Float.valueOf(text);
if (targetType == double.class || targetType == Double.class) return (T) Double.valueOf(text);
} catch (IllegalArgumentException iae) {
throw new IllegalArgumentException(
"Cannot convert \""
+ text
+ "\" to "
+ targetType.getSimpleName().toLowerCase()
);
}
if (targetType == char.class || targetType == Character.class) {
if (text.length() == 0) throw new IllegalArgumentException("Empty string");
if (text.length() > 1) throw new IllegalArgumentException("String too long");
return (T) Character.valueOf(text.charAt(0));
}
if (targetType == char[].class) return (T) text.toCharArray();
if (targetType == Charset.class) return (T) Charset.forName(text);
if (targetType == Class.class) {
try {
return (T) Class.forName(text);
} catch (ClassNotFoundException cnfe) {
throw new IllegalArgumentException(cnfe);
} catch (NoClassDefFoundError ncdfe) {
throw new IllegalArgumentException(ncdfe);
}
}
if (targetType == Pattern.class) return (T) Pattern.compile(text);
if (Enum.class.isAssignableFrom(targetType)) {
try {
@SuppressWarnings("rawtypes") Enum constant = Enum.valueOf((Class) targetType, text);
return (T) constant;
} catch (IllegalArgumentException iae) {
@SuppressWarnings("rawtypes") EnumSet allConstants = EnumSet.allOf((Class) targetType);
throw new IllegalArgumentException(
"Invalid constant \""
+ text
+ "\"; valid values are "
+ allConstants
);
}
}
// For all other parameter types, use the single-string-parameter constructor.
try {
return targetType.getConstructor(String.class).newInstance(text);
} catch (Exception e) {
throw new IllegalArgumentException((
"Instantiating "
+ targetType.getSimpleName()
+ ": "
+ e.getMessage()
), e);
}
}
/**
* This method returns {@code null} although it is declared {@link NotNull @NotNull}. This comes in handy to
* initialize a field that is declared as {@code NotNull @NotNull}, but is filled reflectively, e.g. by
* frameworks like JUNIT or SPRING.
*/
@SuppressWarnings("null") public static T
almostNull() { return null; }
}
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