de.unkrig.commons.lang

Class ObjectUtil

java.lang.Object

de.unkrig.commons.lang.ObjectUtil

public final class ObjectUtil
extends Object

Various java.lang.Object-related utility methods.

Method Summary

Modifier and Type	Method and Description
static <T> T	almostNull() This method returns null although it is declared @NotNull.
static <T> boolean	equals(T o1, T o2) The often-needed "equal" method that handles null references.
static <T> T	fromString(String text, Class<T> targetType) Converts a string to an object of the given targetType.
static int	hashCode(Object o)
static <T> T	or(T lhs, T rhs)
static <T> String	toString(T value, String defaultValue)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

equals

public static <T> boolean equals(@Nullable
                                 T o1,
                                 @Nullable
                                 T o2)

The often-needed "equal" method that handles null references.

Redeemed by java.util.Objects.equals(Object, Object) which is available since Java 1.7.

Returns:

Both arguments are null, or are CharSequences with equal contents, or are equal

hashCode

public static int hashCode(@Nullable
                           Object o)

Returns:

Null iff o == null, otherwise o.hashCode()

toString

public static <T> String toString(@Nullable
                                  T value,
                                  String defaultValue)

Returns:

Returns value.toString() or the defaultValue iff value == null

or

public static <T> T or(@Nullable
                       T lhs,
                       T rhs)

Returns:

lhs, or rhs iff lhs == null

fromString

public static <T> T fromString(String text,
                               Class<T> targetType)

Converts a string to an object of the given targetType.

For primitive targetTypes, the corresponding wrapper object is returned.

Supports all primitive types (except void), their wrapper types, String, char[], Charset, Class, 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 EnumSets, because the element type cannot be determined through REFLECTION. Usage of an array is recommended as a workaround, as follows:

String  s   = "RED,GREEN";
Color[] tmp = ObjectUtil.fromString(s, Color[].class);

List<Color>    list    = Arrays.asList(tmp);
EnumSet<Color> enumSet = EnumSet.copyOf(Arrays.asList(tmp));
Set<Color>     set     = new HashSet<String>(Arrays.asList(tmp));

Throws:

NumberFormatException - The string could not be converted to the targetType

IllegalArgumentException - The string could not be converted to the targetType

RuntimeException - The string could not be converted to the targetType

almostNull

public static <T> T almostNull()

This method returns null although it is declared @NotNull. This comes in handy to initialize a field that is declared as NotNull @NotNull, but is filled reflectively, e.g. by frameworks like JUNIT or SPRING.