net.hasor.cobble

类 ObjectUtils

java.lang.Object

net.hasor.cobble.ObjectUtils

public class ObjectUtils
extends Object

Operations on Object.

This class tries to handle null input gracefully. An exception will generally not be thrown for a null input. Each method documents its behaviour in more detail.

#ThreadSafe#

从以下版本开始:

1.0

版本:

$Id: ObjectUtils.java 1057434 2011-01-11 01:27:37Z niallp $

作者:

Apache Software Foundation, Nissim Karpenstein, Janek Bogucki, Daniel L. Rall, Gary Gregory, Mario Winterer, David J. M. Karlsen

嵌套类概要

嵌套类

限定符和类型	类和说明
static class	ObjectUtils.Null Class used as a null placeholder where null has another meaning.

字段概要

字段

限定符和类型	字段和说明
static ObjectUtils.Null	NULL Singleton used as a null placeholder where null has another meaning.

构造器概要

构造器

构造器和说明
ObjectUtils() ObjectUtils instances should NOT be constructed in standard programming.

方法概要

限定符和类型	方法和说明
static int	checkInRange(int i, int start, int end, String name) Checks that the given argument is in range.
static long	checkInRange(long l, long start, long end, String name) Checks that the given argument is in range.
static <T> T	checkNotNull(T arg, String text) Checks that the given argument is not null.
static int	checkPositive(int i, String name) Checks that the given argument is strictly positive.
static long	checkPositive(long l, String name) Checks that the given argument is strictly positive.
static int	checkPositiveOrZero(int i, String name) Checks that the given argument is positive or zero.
static long	checkPositiveOrZero(long l, String name) Checks that the given argument is positive or zero.
static int	compare(Comparable c1, Comparable c2) Null safe comparison of Comparables.
static int	compare(Comparable c1, Comparable c2, boolean nullGreater) Null safe comparison of Comparables.
static Object	defaultIfNull(Object object, Object defaultValue) Returns a default value if the object passed is null.
static boolean	equals(Object object1, Object object2) Compares two objects for equality, where either one or both objects may be null.
static int	hashCode(Object obj) Gets the hash code of an object returning zero when the object is null.
static String	identityToString(Object object) Gets the toString that would be produced by Object if a class did not override toString itself.
static void	identityToString(StringBuffer buffer, Object object) Appends the toString that would be produced by Object if a class did not override toString itself.
static Object	max(Comparable c1, Comparable c2) Null safe comparison of Comparables.
static Object	min(Comparable c1, Comparable c2) Null safe comparison of Comparables.
static boolean	notEqual(Object object1, Object object2) Compares two objects for inequality, where either one or both objects may be null.
static int	nullSafeHashCode(boolean[] array) Return a hash code based on the contents of the specified array.
static int	nullSafeHashCode(byte[] array) Return a hash code based on the contents of the specified array.
static int	nullSafeHashCode(char[] array) Return a hash code based on the contents of the specified array.
static int	nullSafeHashCode(double[] array) Return a hash code based on the contents of the specified array.
static int	nullSafeHashCode(float[] array) Return a hash code based on the contents of the specified array.
static int	nullSafeHashCode(int[] array) Return a hash code based on the contents of the specified array.
static int	nullSafeHashCode(long[] array) Return a hash code based on the contents of the specified array.
static int	nullSafeHashCode(Object obj) Return as hash code for the given object; typically the value of Object#hashCode()}.
static int	nullSafeHashCode(Object[] array) Return a hash code based on the contents of the specified array.
static int	nullSafeHashCode(short[] array) Return a hash code based on the contents of the specified array.
static String	toString(Object obj) Gets the toString of an Object returning an empty string ("") if null input.
static String	toString(Object obj, String nullStr) Gets the toString of an Object returning a specified text if null input.

从类继承的方法 java.lang.Object

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

字段详细资料

NULL

public static final ObjectUtils.Null NULL

Singleton used as a null placeholder where null has another meaning.

For example, in a HashMap the HashMap.get(Object) method returns null if the Map contains null or if there is no matching key. The Null placeholder can be used to distinguish between these two cases.

Another example is Hashtable, where null cannot be stored.

This instance is Serializable.

构造器详细资料

ObjectUtils

public ObjectUtils()

ObjectUtils instances should NOT be constructed in standard programming. Instead, the class should be used as ObjectUtils.defaultIfNull("a","b");.

This constructor is public to permit tools that require a JavaBean instance to operate.

方法详细资料

defaultIfNull

public static Object defaultIfNull(Object object,
                                   Object defaultValue)

Returns a default value if the object passed is null.

 ObjectUtils.defaultIfNull(null, null)      = null
 ObjectUtils.defaultIfNull(null, "")        = ""
 ObjectUtils.defaultIfNull(null, "zz")      = "zz"
 ObjectUtils.defaultIfNull("abc", *)        = "abc"
 ObjectUtils.defaultIfNull(Boolean.TRUE, *) = Boolean.TRUE
 

参数:

object - the Object to test, may be null

defaultValue - the default value to return, may be null

返回:

object if it is not null, defaultValue otherwise

equals

public static boolean equals(Object object1,
                             Object object2)

Compares two objects for equality, where either one or both objects may be null.

 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
 

参数:

object1 - the first object, may be null

object2 - the second object, may be null

返回:

true if the values of both objects are the same

notEqual

public static boolean notEqual(Object object1,
                               Object object2)

Compares two objects for inequality, where either one or both objects may be null.

 ObjectUtils.notEqual(null, null)                  = false
 ObjectUtils.notEqual(null, "")                    = true
 ObjectUtils.notEqual("", null)                    = true
 ObjectUtils.notEqual("", "")                      = false
 ObjectUtils.notEqual(Boolean.TRUE, null)          = true
 ObjectUtils.notEqual(Boolean.TRUE, "true")        = true
 ObjectUtils.notEqual(Boolean.TRUE, Boolean.TRUE)  = false
 ObjectUtils.notEqual(Boolean.TRUE, Boolean.FALSE) = true
 

参数:

object1 - the first object, may be null

object2 - the second object, may be null

返回:

false if the values of both objects are the same

从以下版本开始:

2.6

hashCode

public static int hashCode(Object obj)

Gets the hash code of an object returning zero when the object is null.

 ObjectUtils.hashCode(null)   = 0
 ObjectUtils.hashCode(obj)    = obj.hashCode()
 

参数:

obj - the object to obtain the hash code of, may be null

返回:

the hash code of the object, or zero if null

从以下版本开始:

2.1

identityToString

public static String identityToString(Object object)

Gets the toString that would be produced by Object if a class did not override toString itself. null will return null.

 ObjectUtils.identityToString(null)         = null
 ObjectUtils.identityToString("")           = "java.lang.String@1e23"
 ObjectUtils.identityToString(Boolean.TRUE) = "java.lang.Boolean@7fa"
 

参数:

object - the object to create a toString for, may be null

返回:

the default toString text, or null if null passed in

identityToString

public static void identityToString(StringBuffer buffer,
                                    Object object)

Appends the toString that would be produced by Object if a class did not override toString itself. null will throw a NullPointerException for either of the two parameters.

 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")
 

参数:

buffer - the buffer to append to

object - the object to create a toString for

从以下版本开始:

2.4

toString

public static String toString(Object obj)

Gets the toString of an Object returning an empty string ("") if null input.

 ObjectUtils.toString(null)         = ""
 ObjectUtils.toString("")           = ""
 ObjectUtils.toString("bat")        = "bat"
 ObjectUtils.toString(Boolean.TRUE) = "true"
 

参数:

obj - the Object to toString, may be null

返回:

the passed in Object's toString, or nullStr if null input

从以下版本开始:

2.0

另请参阅:

StringUtils.defaultString(String), String.valueOf(Object)

toString

public static String toString(Object obj,
                              String nullStr)

Gets the toString of an Object returning a specified text if null input.

 ObjectUtils.toString(null, null)           = null
 ObjectUtils.toString(null, "null")         = "null"
 ObjectUtils.toString("", "null")           = ""
 ObjectUtils.toString("bat", "null")        = "bat"
 ObjectUtils.toString(Boolean.TRUE, "null") = "true"
 

参数:

obj - the Object to toString, may be null

nullStr - the String to return if null input, may be null

返回:

the passed in Object's toString, or nullStr if null input

从以下版本开始:

2.0

另请参阅:

StringUtils.defaultString(String, String), String.valueOf(Object)

min

public static Object min(Comparable c1,
                         Comparable c2)

Null safe comparison of Comparables.

参数:

c1 - the first comparable, may be null

c2 - the second comparable, may be null

返回:

• If both objects are non-null and unequal, the lesser object.
• If both objects are non-null and equal, c1.
• If one of the comparables is null, the non-null object.
• If both the comparables are null, null is returned.

max

public static Object max(Comparable c1,
                         Comparable c2)

Null safe comparison of Comparables.

参数:

c1 - the first comparable, may be null

c2 - the second comparable, may be null

返回:

• If both objects are non-null and unequal, the greater object.
• If both objects are non-null and equal, c1.
• If one of the comparables is null, the non-null object.
• If both the comparables are null, null is returned.

compare

public static int compare(Comparable c1,
                          Comparable c2)

Null safe comparison of Comparables. null is assumed to be less than a non-null value.

参数:

c1 - the first comparable, may be null

c2 - the second comparable, may be null

返回:

a negative value if c1 < c2, zero if c1 = c2 and a positive value if c1 > c2

从以下版本开始:

2.6

compare

public static int compare(Comparable c1,
                          Comparable c2,
                          boolean nullGreater)

Null safe comparison of Comparables.

参数:

c1 - the first comparable, may be null

c2 - the second comparable, may be null

nullGreater - if true null is considered greater than a Non-null value or if false null is considered less than a Non-null value

返回:

a negative value if c1 < c2, zero if c1 = c2 and a positive value if c1 > c2

从以下版本开始:

2.6

另请参阅:

Comparator.compare(Object, Object)

nullSafeHashCode

public static int nullSafeHashCode(Object obj)

Return as hash code for the given object; typically the value of Object#hashCode()}. If the object is an array, this method will delegate to any of the nullSafeHashCode methods for arrays in this class. If the object is null, this method returns 0.

另请参阅:

Object.hashCode(), nullSafeHashCode(Object[]), nullSafeHashCode(boolean[]), nullSafeHashCode(byte[]), nullSafeHashCode(char[]), nullSafeHashCode(double[]), nullSafeHashCode(float[]), nullSafeHashCode(int[]), nullSafeHashCode(long[]), nullSafeHashCode(short[])

nullSafeHashCode

public static int nullSafeHashCode(Object[] array)

Return a hash code based on the contents of the specified array. If array is null, this method returns 0.

nullSafeHashCode

public static int nullSafeHashCode(boolean[] array)

Return a hash code based on the contents of the specified array. If array is null, this method returns 0.

nullSafeHashCode

public static int nullSafeHashCode(byte[] array)

Return a hash code based on the contents of the specified array. If array is null, this method returns 0.

nullSafeHashCode

public static int nullSafeHashCode(char[] array)

Return a hash code based on the contents of the specified array. If array is null, this method returns 0.

nullSafeHashCode

public static int nullSafeHashCode(double[] array)

Return a hash code based on the contents of the specified array. If array is null, this method returns 0.

nullSafeHashCode

public static int nullSafeHashCode(float[] array)

Return a hash code based on the contents of the specified array. If array is null, this method returns 0.

nullSafeHashCode

public static int nullSafeHashCode(int[] array)

Return a hash code based on the contents of the specified array. If array is null, this method returns 0.

nullSafeHashCode

public static int nullSafeHashCode(long[] array)

Return a hash code based on the contents of the specified array. If array is null, this method returns 0.

nullSafeHashCode

public static int nullSafeHashCode(short[] array)

Return a hash code based on the contents of the specified array. If array is null, this method returns 0.

checkNotNull

public static <T> T checkNotNull(T arg,
                                 String text)

Checks that the given argument is not null. If it is, throws NullPointerException. Otherwise, returns the argument.

checkPositive

public static int checkPositive(int i,
                                String name)

Checks that the given argument is strictly positive. If it is not, throws IllegalArgumentException. Otherwise, returns the argument.

checkPositive

public static long checkPositive(long l,
                                 String name)

Checks that the given argument is strictly positive. If it is not, throws IllegalArgumentException. Otherwise, returns the argument.

checkPositiveOrZero

public static int checkPositiveOrZero(int i,
                                      String name)

Checks that the given argument is positive or zero. If it is not , throws IllegalArgumentException. Otherwise, returns the argument.

checkPositiveOrZero

public static long checkPositiveOrZero(long l,
                                       String name)

Checks that the given argument is positive or zero. If it is not, throws IllegalArgumentException. Otherwise, returns the argument.

checkInRange

public static int checkInRange(int i,
                               int start,
                               int end,
                               String name)

Checks that the given argument is in range. If it is not, throws IllegalArgumentException. Otherwise, returns the argument.

checkInRange

public static long checkInRange(long l,
                                long start,
                                long end,
                                String name)

Checks that the given argument is in range. If it is not, throws IllegalArgumentException. Otherwise, returns the argument.