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java.lang.reflect

Class Array

public final class Array
extends Object
Array holds static helper functions that allow you to create and manipulate arrays by reflection. Operations know how to perform widening conversions, but throw IllegalArgumentException if you attempt a narrowing conversion. Also, when accessing primitive arrays, this class performs object wrapping and unwrapping as necessary.

Note: This class returns and accepts types as Classes, even primitive types; there are Class types defined that represent each different primitive type. They are java.lang.Boolean.TYPE, java.lang.Byte.TYPE,, also available as boolean.class, byte.class, etc. These are not to be confused with the classes java.lang.Boolean, java.lang.Byte, etc., which are real classes. Note also that the shorthand Object[].class is a convenient way to get array Classes.

Performance note: This class performs best when it does not have to convert primitive types. The further along the chain it has to convert, the worse performance will be. You're best off using the array as whatever type it already is, and then converting the result. You will do even worse if you do this and use the generic set() function.

Since:
1.1
See Also:
Boolean.TYPE, Byte.TYPE, Short.TYPE, Character.TYPE, Integer.TYPE, Long.TYPE, Float.TYPE, Double.TYPE

Method Summary

static Object
get(Object array, int index)
Gets an element of an array.
static boolean
getBoolean(Object array, int index)
Gets an element of a boolean array.
static byte
getByte(Object array, int index)
Gets an element of a byte array.
static char
getChar(Object array, int index)
Gets an element of a char array.
static double
getDouble(Object array, int index)
Gets an element of a double array.
static float
getFloat(Object array, int index)
Gets an element of a float array.
static int
getInt(Object array, int index)
Gets an element of an int array.
static int
getLength(Object array)
Gets the array length.
static long
getLong(Object array, int index)
Gets an element of a long array.
static short
getShort(Object array, int index)
Gets an element of a short array.
static Object
newInstance(Class componentType, int length)
Creates a new single-dimensioned array.
static Object
newInstance(Class componentType, int[] dimensions)
Creates a new multi-dimensioned array.
static void
set(Object array, int index, Object value)
Sets an element of an array.
static void
setBoolean(Object array, int index, boolean value)
Sets an element of a boolean array.
static void
setByte(Object array, int index, byte value)
Sets an element of a byte array.
static void
setChar(Object array, int index, char value)
Sets an element of a char array.
static void
setDouble(Object array, int index, double value)
Sets an element of a double array.
static void
setFloat(Object array, int index, float value)
Sets an element of a float array.
static void
setInt(Object array, int index, int value)
Sets an element of an int array.
static void
setLong(Object array, int index, long value)
Sets an element of a long array.
static void
setShort(Object array, int index, short value)
Sets an element of a short array.

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

get

public static Object get(Object array,
                         int index)
Gets an element of an array. Primitive elements will be wrapped in the corresponding class type.
Parameters:
array - the array to access
index - the array index to access
Returns:
the element at array[index]
Throws:
IllegalArgumentException - if array is not an array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
getBoolean(Object,int), getByte(Object,int), getChar(Object,int), getShort(Object,int), getInt(Object,int), getLong(Object,int), getFloat(Object,int), getDouble(Object,int)

getBoolean

public static boolean getBoolean(Object array,
                                 int index)
Gets an element of a boolean array.
Parameters:
array - the array to access
index - the array index to access
Returns:
the boolean element at array[index]
Throws:
IllegalArgumentException - if array is not a boolean array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
get(Object,int)

getByte

public static byte getByte(Object array,
                           int index)
Gets an element of a byte array.
Parameters:
array - the array to access
index - the array index to access
Returns:
the byte element at array[index]
Throws:
IllegalArgumentException - if array is not a byte array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
get(Object,int)

getChar

public static char getChar(Object array,
                           int index)
Gets an element of a char array.
Parameters:
array - the array to access
index - the array index to access
Returns:
the char element at array[index]
Throws:
IllegalArgumentException - if array is not a char array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
get(Object,int)

getDouble

public static double getDouble(Object array,
                               int index)
Gets an element of a double array.
Parameters:
array - the array to access
index - the array index to access
Returns:
the double element at array[index]
Throws:
IllegalArgumentException - if array is not a byte, char, short, int, long, float, or double array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
get(Object,int)

getFloat

public static float getFloat(Object array,
                             int index)
Gets an element of a float array.
Parameters:
array - the array to access
index - the array index to access
Returns:
the float element at array[index]
Throws:
IllegalArgumentException - if array is not a byte, char, short, int, long, or float array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
get(Object,int)

getInt

public static int getInt(Object array,
                         int index)
Gets an element of an int array.
Parameters:
array - the array to access
index - the array index to access
Returns:
the int element at array[index]
Throws:
IllegalArgumentException - if array is not a byte, char, short, or int array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
get(Object,int)

getLength

public static int getLength(Object array)
Gets the array length.
Parameters:
array - the array
Returns:
the length of the array
Throws:
IllegalArgumentException - if array is not an array
NullPointerException - if array is null

getLong

public static long getLong(Object array,
                           int index)
Gets an element of a long array.
Parameters:
array - the array to access
index - the array index to access
Returns:
the long element at array[index]
Throws:
IllegalArgumentException - if array is not a byte, char, short, int, or long array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
get(Object,int)

getShort

public static short getShort(Object array,
                             int index)
Gets an element of a short array.
Parameters:
array - the array to access
index - the array index to access
Returns:
the short element at array[index]
Throws:
IllegalArgumentException - if array is not a byte or char array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
get(Object,int)

newInstance

public static Object newInstance(Class componentType,
                                 int length)
Creates a new single-dimensioned array.
Parameters:
componentType - the type of the array to create
length - the length of the array to create
Returns:
the created array, cast to an Object
Throws:
NullPointerException - if componentType is null
IllegalArgumentException - if componentType is Void.TYPE
NegativeArraySizeException - when length is less than 0

newInstance

public static Object newInstance(Class componentType,
                                 int[] dimensions)
Creates a new multi-dimensioned array. The new array has the same component type as the argument class, and the number of dimensions in the new array is the sum of the dimensions of the argument class and the length of the argument dimensions. Virtual Machine limitations forbid too many dimensions (usually 255 is the maximum); but even 50 dimensions of 2 elements in each dimension would exceed your memory long beforehand!
Parameters:
componentType - the type of the array to create.
dimensions - the dimensions of the array to create. Each element in dimensions makes another dimension of the new array. Thus, Array.newInstance(java.lang.Boolean, new int[]{1,2,3}) is the same as new java.lang.Boolean[1][2][3]
Returns:
the created array, cast to an Object
Throws:
NullPointerException - if componentType or dimension is null
IllegalArgumentException - if the the size of dimensions is 0 or exceeds the maximum number of array dimensions in the VM; or if componentType is Void.TYPE
NegativeArraySizeException - when any of the dimensions is less than 0

set

public static void set(Object array,
                       int index,
                       Object value)
Sets an element of an array. If the array is primitive, then the new value is unwrapped and widened.
Parameters:
array - the array to set a value of
index - the array index to set the value to
value - the value to set
Throws:
IllegalArgumentException - if array is not an array, or the array is primitive and unwrapping value fails, or the value is not assignable to the array component type
NullPointerException - if array is null, or if array is primitive and value is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
setBoolean(Object,int,boolean), setByte(Object,int,byte), setChar(Object,int,char), setShort(Object,int,short), setInt(Object,int,int), setLong(Object,int,long), setFloat(Object,int,float), setDouble(Object,int,double)

setBoolean

public static void setBoolean(Object array,
                              int index,
                              boolean value)
Sets an element of a boolean array.
Parameters:
array - the array to set a value of
index - the array index to set the value to
value - the value to set
Throws:
IllegalArgumentException - if array is not a boolean array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
set(Object,int,Object)

setByte

public static void setByte(Object array,
                           int index,
                           byte value)
Sets an element of a byte array.
Parameters:
array - the array to set a value of
index - the array index to set the value to
value - the value to set
Throws:
IllegalArgumentException - if array is not a byte, short, int, long, float, or double array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
set(Object,int,Object)

setChar

public static void setChar(Object array,
                           int index,
                           char value)
Sets an element of a char array.
Parameters:
array - the array to set a value of
index - the array index to set the value to
value - the value to set
Throws:
IllegalArgumentException - if array is not a char, int, long, float, or double array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
set(Object,int,Object)

setDouble

public static void setDouble(Object array,
                             int index,
                             double value)
Sets an element of a double array.
Parameters:
array - the array to set a value of
index - the array index to set the value to
value - the value to set
Throws:
IllegalArgumentException - if array is not a double array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
set(Object,int,Object)

setFloat

public static void setFloat(Object array,
                            int index,
                            float value)
Sets an element of a float array.
Parameters:
array - the array to set a value of
index - the array index to set the value to
value - the value to set
Throws:
IllegalArgumentException - if array is not a float or double array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
set(Object,int,Object)

setInt

public static void setInt(Object array,
                          int index,
                          int value)
Sets an element of an int array.
Parameters:
array - the array to set a value of
index - the array index to set the value to
value - the value to set
Throws:
IllegalArgumentException - if array is not an int, long, float, or double array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
set(Object,int,Object)

setLong

public static void setLong(Object array,
                           int index,
                           long value)
Sets an element of a long array.
Parameters:
array - the array to set a value of
index - the array index to set the value to
value - the value to set
Throws:
IllegalArgumentException - if array is not a long, float, or double array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
set(Object,int,Object)

setShort

public static void setShort(Object array,
                            int index,
                            short value)
Sets an element of a short array.
Parameters:
array - the array to set a value of
index - the array index to set the value to
value - the value to set
Throws:
IllegalArgumentException - if array is not a short, int, long, float, or double array
NullPointerException - if array is null
ArrayIndexOutOfBoundsException - if index is out of bounds
See Also:
set(Object,int,Object)
java.lang.reflect.Array - manipulate arrays by reflection Copyright (C) 1998, 1999, 2001, 2003, 2005 Free Software Foundation, Inc. This file is part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GNU Classpath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.

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