Download int int - DiSpace

Рефлексия
Макаревич Л. Г.
Introspection и reflection
Самоанализ и рефлексия
(java.lang.Class, java.lang.reflect)
 Получение информации о методах,
полях классов, динамическое
создание объектов и классов

Основные возможности
рефлексии
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Определить тип объекта
Получить данные о методах, полях,
конструкторах, родительском типе,
модификаторах
Выделить методы и константы интерфейса
Создать объекты заранее неизвестного
типа
Получить.установить значения полей
Вызвать метод
Создать массив объектов неизвестного
типа, изменять значения элементов
Использование instanceof
class A
{
int i;
A(int j){i = j;}
}
class B extends A
{
int k;
B(int j){super(j); k = j+1;}
static public void main(String [] arg)
{
A a1 = new A(88);
B b1 = new B(55);
System.out.println(b1 instanceof A); //true
System.out.println(a1 instanceof B); //false
System.out.println(c.isInstance(a1)); //true
System.out.println(c.isInstance(b1)); //true
System.out.println(c.isInstance(a1)); //false
}
}
Получение имени класса
По ссылке на объект
Class c =mystery.getClass();// в Object
 Родительский класс
JTextField t = new JTextField();
Class c = t.getClass();
Class cp = c.getSuperClass();
 На стадии компиляции по имени класса
Class c = Jbutton.class;
Class c = boolean.class;
Class c = int.class;
Class c = Boolean.TYPE; // эквивалентно boolean.class
 На стадии выполнения по имени класса
Class c = Class.forName(nameOfClass);

import java.lang.*;
import java.lang.reflect.*;
class C
{
public int a;
private int b;
public static void main(String [] arg)
{
C m = new C();
class C
int
try
{
System.out.println(Class.forName("C"));
int
Class c1 = int.class;
System.out.println(c1);
System.out.println(c1.getName());
c1= Integer.class;
System.out.println(c1.getName());
c1 = Integer.TYPE;
System.out.println(c1.getName());
System.out.println(int.class.getName());
}catch(Exception e){}
String s = new String();
Class c = m.getClass();
Class sc = c.getSuperclass();
}
}
java.lang.Integer
int
int
Определение интерфейсов
класса
Class[]
getInterfaces()
Determines the interfaces implemented by the class or interface represented by this object.
boolean
isInterface()
Determines if the specified Class object represents an interface type.
import java.lang.reflect.*;
import java.io.*;
interface A
{
int aa(int a);
}
class SampleInterface implements A
{ public static void main(String[] args) {
SampleInterface s = new SampleInterface();
printInterfaceNames(s);
Class o = A.class;
if (o.isInterface())
System.out.println(o.getName() + “ is interface");
else
System.out.println(o.getName() + “ is class");
o = s.getClass();
}
public int aa(int a){ return a++;}
static void printInterfaceNames(Object o) {
Class[] theInterfaces = c.getInterfaces();
for (int i = 0; i < theInterfaces.length; i++) {
String interfaceName = theInterfaces[i].getName();
System.out.println(interfaceName);
}
}
}
A
A is interface
interface A
{
int aa(int a);
}
class SampleInterface implements A
{ public static void main(String[] args) {
RandomAccessFile r;
try {
r = new RandomAccessFile("int.java", "r");
SampleInterface.printInterfaceNames(r);
} catch (IOException e) {
System.out.println(e);
}
}
public int aa(int a){ return a++;}
static void printInterfaceNames(Object o) {
Class c = o.getClass();
Class[] theInterfaces = c.getInterfaces();
for (int i = 0; i < theInterfaces.length; i++) {
String interfaceName = theInterfaces[i].getName();
System.out.println(interfaceName);
}
}
}
java.io.DataOutput
java.io.DataInput
Модификаторы класса
Class Modifier
static boolean
static boolean
static boolean
static boolean
static boolean
static boolean
static boolean
static boolean
static boolean
isAbstract(int mod)
Return true if the integer argument includes the abstract modifer, false otherwise.
isFinal(int mod)
Return true if the integer argument includes the final modifer, false otherwise.
isInterface(int mod)
Return true if the integer argument includes the interface modifer, false otherwise.
isNative(int mod)
Return true if the integer argument includes the native modifer, false otherwise.
isPrivate(int mod)
Return true if the integer argument includes the private modifer, false otherwise.
isProtected(int mod)
Return true if the integer argument includes the protected modifer, false otherwise.
isPublic(int mod)
Return true if the integer argument includes the public modifer, false otherwise.
isStatic(int mod)
Return true if the integer argument includes the static modifer, false otherwise.
isStrict(int mod)
Return true if the integer argument includes the strictfp modifer, false otherwise.
static boolean
isSynchronized(int mod)
Return true if the integer argument includes the synchronized modifer, false otherwise.
static boolean
isTransient(int mod)
Return true if the integer argument includes the transient modifer, false otherwise.
static boolean
isVolatile(int mod)
Return true if the integer argument includes the volatile modifer, false otherwise.
toString(int mod)
static String
Return a string describing the access modifier flags in the specified modifier.
static int
ABSTRACT
The int value representing the abstract modifier.
static int
FINAL
The int value representing the final modifier.
static int
INTERFACE
The int value representing the interface modifier.
static int
NATIVE
The int value representing the native modifier.
static int
PRIVATE
The int value representing the private modifier.
static int
PROTECTED
The int value representing the protected modifier.
static int
PUBLIC
The int value representing the public modifier.
static int
STATIC
The int value representing the static modifier.
static int
STRICT
The int value representing the strictfp modifier.
static int
SYNCHRONIZED
The int value representing the synchronized modifier.
static int
TRANSIENT
The int value representing the transient modifier.
static int
VOLATILE
The int value representing the volatile modifier.
Класс Class
int
getModifiers()
Returns the Java language modifiers for this class or interface, encoded in an integer.
import java.lang.reflect.*;
class My
{public static void main(String [] arg)
{ My m = new My();
try{
System.out.println(Class.forName("My"));
}catch(Exception e){}
String s=new String();
printModifiers(s);
/*****************************/
Class c = m.getClass();
Class sc = c.getSuperclass();
while (sc != null) {
class My
String className = sc.getName();
public
System.out.println(className);
final
c = sc;
sc = c.getSuperclass();
}
}
public static void printModifiers(Object o) {
Class c = o.getClass();
int m = c.getModifiers();
if (Modifier.isPublic(m))
System.out.println("public");
if (Modifier.isAbstract(m))
System.out.println("abstract");
if (Modifier.isFinal(m))
System.out.println("final");
} }
java.lang.Object
Конструкторы
boole
an
equals(Object obj)
Class
getDeclaringClass()
Class Constructor
Compares this Constructor against the specified object.
Returns the Class object representing the class that declares the constructor represented by this Constructor object.
Class
[]
int
getExceptionTypes()
Returns an array of Class objects that represent the types of of exceptions declared to be thrown by the underlying constructor
represented by this Constructor object.
getModifiers()
Returns the Java language modifiers for the constructor represented by this Constructor object, as an integer.
String
getName()
Returns the name of this constructor, as a string.
Class
[]
int
getParameterTypes()
Returns an array of Class objects that represent the formal parameter types, in declaration order, of the constructor represented by
this Constructor object.
hashCode()
Returns a hashcode for this Constructor.
Objec
t
newInstance(Object[] initargs)
String
toString()
Uses the constructor represented by this Constructor object to create and initialize a new instance of the constructor's declaring
class, with the specified initialization parameters.
Returns a string describing this Constructor
Класс Class
Const getConstructor(Class[] parameterTypes)
Returns a Constructor object that reflects the specified public constructor of the
ructor
class represented by this Class object.
Const getConstructors()
ructor[]
Returns an array containing Constructor objects reflecting all the public
constructors of the class represented by this Class object.
Class[ getDeclaredClasses()
]
Returns an array of Class objects reflecting all the classes and interfaces
declared as members of the class represented by this Class object.
Const getDeclaredConstructor(Class[] parameterTypes)
Returns a Constructor object that reflects the specified constructor of the class
ructor
or interface represented by this Class object.
Const getDeclaredConstructors()
Returns an array of Constructor objects reflecting all the constructors declared
ructor[]
by the class represented by this Class object.
import java.lang.reflect.*;
import java.awt.*;
class SampleConstructor {
public static void main(String[] args) {
Rectangle r = new Rectangle();
showConstructors(r);
}
static void showConstructors(Object o) {
Class c = o.getClass();
( java.awt.Point java.awt.Dimension )
Constructor[] theConstructors = c.getConstructors();
()
for (int i = 0; i < theConstructors.length; i++) {
( java.awt.Rectangle )
System.out.print("( ");
( int int int int )
Class[] parameterTypes =
theConstructors[i].getParameterTypes();
for (int k = 0; k < parameterTypes.length; k ++) {
String parameterString = parameterTypes[k].getName();
System.out.print(parameterString + " ");
}
System.out.println(")");
}
}
}
( int int )
( java.awt.Point )
( java.awt.Dimension )
Класс Method
boole
an
equals(Object obj)
Class
getDeclaringClass()
Compares this Method against the specified object.
Returns the Class object representing the class or interface that declares the method represented by this Method object.
Class[
]
int
getExceptionTypes()
Returns an array of Class objects that represent the types of the exceptions declared to be thrown by the underlying method
represented by this Method object.
getModifiers()
Returns the Java language modifiers for the method represented by this Method object, as an integer.
String
getName()
Returns the name of the method represented by this Method object, as a String.
Class[
]
getParameterTypes()
Class
getReturnType()
Returns an array of Class objects that represent the formal parameter types, in declaration order, of the method represented by
this Method object.
Returns a Class object that represents the formal return type of the method represented by this Method object.
int
hashCode()
Returns a hashcode for this Method.
Objec
t
invoke(Object obj, Object[] args)
String
toString()
Invokes the underlying method represented by this Method object, on the specified object with the specified parameters.
Returns a string describing this Method.
Класс Class
Method
getDeclaredMethod(String name, Class[] parameterTypes)
Returns a Method object that reflects the specified declared method of the class or interface represented by this Class object.
Method[
]
Method
getDeclaredMethods()
Returns an array of Method objects reflecting all the methods declared by the class or interface represented by this Class object.
getMethod(String name, Class[] parameterTypes)
Returns a Method object that reflects the specified public member method of the class or interface represented by this Class
object.
Method
[]
getMethods()
Returns an array containing Method objects reflecting all the public member methods of the class or interface represented by this Class
object, including those declared by the class or interface and and those inherited from superclasses and superinterfaces.
import java.lang.reflect.*;
import java.awt.*;
class SampleMethod {
public static void main(String[] args) {
Object p = new Object();
showMethods(p);
}
static void showMethods(Object o) {
Class c = o.getClass();
Method[] theMethods = c.getMethods();
for (int i = 0; i < theMethods.length; i++) {
String methodString = theMethods[i].getName();
System.out.println("Name: " + methodString);
String returnString =
theMethods[i].getReturnType().getName();
System.out.println(" Return Type: " + returnString);
Class[] parameterTypes = theMethods[i].getParameterTypes();
System.out.print(" Parameter Types:");
for (int k = 0; k < parameterTypes.length; k ++) {
String parameterString = parameterTypes[k].getName();
System.out.print(" " + parameterString);
}
System.out.println();
} } }
Name: hashCode
Return Type: int
Parameter Types:
Name: getClass
Return Type: java.lang.Class
Parameter Types:
Name: wait
Return Type: void
Parameter Types: long int
Name: wait
Return Type: void
Parameter Types:
Name: wait
Return Type: void
Parameter Types: long
Name: equals
Return Type: boolean
Parameter Types: java.lang.Object
Name: toString
Return Type: java.lang.String
Parameter Types:
Name: notify
Return Type: void
Parameter Types:
Name: notifyAll
Return Type: void
Parameter Types:
Класс Field
boole
an
Object
equals(Object obj)
Compares this Field against the specified object.
get(Object obj)
Returns the value of the field represented by this Field, on the specified object.
boole
an
byte
getBoolean(Object obj)
Gets the value of a static or instance boolean field.
getByte(Object obj)
Gets the value of a static or instance byte field.
char
getChar(Object obj)
Gets the value of a static or instance field of type char or of another primitive type convertible to type char via a widening
conversion.
Class
getDeclaringClass()
Returns the Class object representing the class or interface that declares the field represented by this Field object.
doubl
e
float
getDouble(Object obj)
Gets the value of a static or instance field of type double or of another primitive type convertible to type double via a widening
conversion.
getFloat(Object obj)
Gets the value of a static or instance field of type float or of another primitive type convertible to type float via a widening
conversion
int
long
int
getInt(Object obj)
Gets the value of a static or instance field of type int or of another primitive type convertible to type int via a widening conversion.
getLong(Object obj)
Gets the value of a static or instance field of type long or of another primitive type convertible to type long via a widening
conversion.
getModifiers()
Returns the Java language modifiers for the field represented by this Field object, as an integer.
Strin
g
getName()
short
getShort(Object obj)
Clas
s
getType()
int
Returns the name of the field represented by this Field object.
Gets the value of a static or instance field of type short or of another primitive type convertible to type short via a widening
conversion.
Returns a Class object that identifies the declared type for the field represented by this Field object.
hashCode()
Returns a hashcode for this Field.
void
set(Object obj, Object value)
void
setBoolean(Object obj, boolean z)
void
setByte(Object obj, byte b)
void
setChar(Object obj, char c)
void
setDouble(Object obj, double d)
void
setFloat(Object obj, float f)
void
setInt(Object obj, int i)
void
setLong(Object obj, long l)
void
setShort(Object obj, short s)
Strin
g
toString()
Sets the field represented by this Field object on the specified object argument to the specified new value.
Sets the value of a field as a boolean on the specified object.
Sets the value of a field as a byte on the specified object.
Sets the value of a field as a char on the specified object.
Sets the value of a field as a double on the specified object.
Sets the value of a field as a float on the specified object.
Sets the value of a field as an int on the specified object.
Sets the value of a field as a long on the specified object.
Sets the value of a field as a short on the specified object.
Returns a string describing this Field.
Класс Class
Field
getField(String name)
Returns a Field object that reflects the specified public member field of the class or interface represented by this Class object.
Field[
]
getFields()
Returns an array containing Field objects reflecting all the accessible public fields of the class or interface represented by this
Class object.
import java.lang.reflect.*;
import java.awt.*;
class A
{
public int i, j;
{
i = 55; j = 66;
}
}
class SampleGet {
public static void main(String[] args)throws Exception {
A r = new A();
Class c = r.getClass();
Field f;
Integer value;
f = c.getField("i");
f.set(r, new Integer(99));
f = c.getField("i");
value = (Integer) f.get(r);
System.out.println("I: " + value.toString());
}
}
I: 99
import java.lang.reflect.*;
import java.awt.*;
class SampleField {
public static void main(String[] args) {
Button g = new Button("aaaaa");
printFieldNames(g);
}
static void printFieldNames(Object o) {
Class c = o.getClass();
Field[] publicFields = c.getFields();
for (int i = 0; i < publicFields.length; i++) {
String fieldName = publicFields[i].getName();
Class typeClass = publicFields[i].getType();
String fieldType = typeClass.getName();
System.out.println("Name: " + fieldName +
", Type: " + fieldType);
}
java.awt.Component
System.out.println("************* ");
Class s = c.getSuperclass();
publicFields = s.getFields();
for (int i = 0; i < publicFields.length; i++) {
String fieldName = publicFields[i].getName();
Class typeClass = publicFields[i].getType();
String fieldType = typeClass.getName();
System.out.println("Name: " + fieldName +
", Type: " + fieldType);
}
}
}
Name: TOP_ALIGNMENT, Type: float
Name: CENTER_ALIGNMENT, Type: float
Name: BOTTOM_ALIGNMENT, Type: float
Name: LEFT_ALIGNMENT, Type: float
Name: RIGHT_ALIGNMENT, Type: float
Name: WIDTH, Type: int
Name: HEIGHT, Type: int
Name: PROPERTIES, Type: int
Name: SOMEBITS, Type: int
Name: FRAMEBITS, Type: int
Name: ALLBITS, Type: int
Name: ERROR, Type: int
Name: ABORT, Type: int
*************
Name: TOP_ALIGNMENT, Type: float
Name: CENTER_ALIGNMENT, Type: float
Name: BOTTOM_ALIGNMENT, Type: float
Name: LEFT_ALIGNMENT, Type: float
Name: RIGHT_ALIGNMENT, Type: float
Name: WIDTH, Type: int
Name: HEIGHT, Type: int
Name: PROPERTIES, Type: int
Name: SOMEBITS, Type: int
Name: FRAMEBITS, Type: int
Name: ALLBITS, Type: int
Name: ERROR, Type: int
Name: ABORT, Type: int
import java.lang.reflect.*;
import java.awt.*;
class SampleSet {
public static void main(String[] args) {
Rectangle r = new Rectangle(100, 20);
System.out.println("original: " + r.toString());
modifyWidth(r, new Integer(300));
System.out.println("modified: " + r.toString());
}
static void modifyWidth(Rectangle r, Integer widthParam ) {
Field widthField;
Integer widthValue;
Class c = r.getClass();
try {
widthField = c.getField("width");
widthField.set(r, widthParam);
} catch (NoSuchFieldException e) {
System.out.println(e);
} catch (IllegalAccessException e) {
System.out.println(e);
}
}
}
original: java.awt.Rectangle[x=0,y=0,width=100,height=20]
modified: java.awt.Rectangle[x=0,y=0,width=300,height=20]
import java.lang.reflect.*;
class SampleInvoke {
public static void main(String[] args) {
Выполнение методов
String firstWord = "Hello ";
String secondWord = "everybody.";
String bothWords = append(firstWord, secondWord);
System.out.println(bothWords);
}
public static String append(String firstWord, String
secondWord) {
String result = null;
Class c = String.class;
Class[] parameterTypes = new Class[] {String.class};
Method concatMethod;
Object[] arguments = new Object[] {secondWord};
try {
concatMethod = c.getMethod("concat", parameterTypes);
result = (String) concatMethod.invoke(firstWord,
arguments);
} catch (NoSuchMethodException e) {
System.out.println(e);
} catch (IllegalAccessException e) {
System.out.println(e);
} catch (InvocationTargetException e) {
System.out.println(e);
}
return result;
}
}
Hello everybody.
Динамическое создание объектов
Использование конструктора без
параметров
Класс Class

Object
newInstance()
Creates a new instance of the class represented by this
Class object.

Использование конструктора с
параметрами



Создать объект Class
Создать объект Constructor, используя
getConstructor() класса Class
Использовать метод newInstance с параметром
Object[] из класса Constructor
Использование конструктора без
параметров
import java.lang.reflect.*;
import java.awt.*;
class SampleNoArg {
public static void main(String[] args) {
Rectangle r = (Rectangle) createObject("java.awt.Rectangle");
System.out.println(r.toString());
}
java.awt.Rectangle[x=0,y=0,width=0,height=
static Object createObject(String className) {
0]
Object object = null;
try {
Class classDefinition = Class.forName(className);
object = classDefinition.newInstance();
} catch (InstantiationException e) {
System.out.println(e);
} catch (IllegalAccessException e) {
System.out.println(e);
} catch (ClassNotFoundException e) {
System.out.println(e);
}
return object; } }
Конструктор с параметрами
import java.lang.reflect.*;
import java.awt.*;
class SampleInstance {
public static void main(String[] args) {
Rectangle rectangle;
Class rectangleDefinition;
Class[] intArgsClass = new Class[] {int.class, int.class}; 2
Integer height = new Integer(12);
Integer width = new Integer(34);
Object[] intArgs = new Object[] {height, width}; 3
Constructor intArgsConstructor;
try {
rectangleDefinition = Class.forName("java.awt.Rectangle");
intArgsConstructor =
rectangleDefinition.getConstructor(intArgsClass);
2
rectangle =
(Rectangle) createObject(intArgsConstructor, intArgs);
} catch (Exception e) {
System.out.println(e);
}
}
public static Object createObject(Constructor constructor,
Object[] arguments) {
System.out.println ("Constructor: " + constructor.toString());
Object object = null;
try {
3
object = constructor.newInstance(arguments);
System.out.println ("Object: " + object.toString());
} catch (Exception e) {
System.out.println(e);
}
return object;
}
}
1
Constructor: public java.awt.Rectangle(int,int)
Object: java.awt.Rectangle[x=0,y=0,width=12,height=34]
Определение массива
import java.lang.reflect.*;
import java.awt.*;
class SampleArray {
class KeyPad {
public static void main(String[] args) {
KeyPad target = new KeyPad();
public boolean alive;
printArrayNames(target);
public Button power;
}
public Button[] letters;
static void printArrayNames(Object target) {
public int[] codes;
Class targetClass = target.getClass();
public TextField[] rows;
Field[] publicFields = targetClass.getFields();
public boolean[] states;
for (int i = 0; i < publicFields.length; i++) {
String fieldName = publicFields[i].getName();
}
Class typeClass = publicFields[i].getType();
String fieldType = typeClass.getName();
if (typeClass.isArray()) {
System.out.println("Name: " + fieldName +
", Type: " + fieldType);
}
}
}
}
Name: letters, Type: [Ljava.awt.Button;
Name: codes, Type: [I
Name: rows, Type: [Ljava.awt.TextField;
Name: states, Type: [Z
Определение типа компонентов
массива
import java.lang.reflect.*;
import java.awt.*;
class SampleComponent {
public static void main(String[] args) {
int[] ints = new int[2];
Array: [I, Component: int
Button[] buttons = new Button[6];
Array: [Ljava.awt.Button;, Component: java.awt.Button
String[][] twoDim = new String[4][5];
printComponentType(ints);
Array: [[Ljava.lang.String;, Component: [Ljava.lang.String;
printComponentType(buttons);
printComponentType(twoDim);
}
static void printComponentType(Object array) {
Class arrayClass = array.getClass();
String arrayName = arrayClass.getName();
Class componentClass = arrayClass.getComponentType();
String componentName = componentClass.getName();
System.out.println("Array: " + arrayName +
", Component: " + componentName);
}
}
Значения элементов массива
import java.lang.reflect.*;
class SampleGetArray {
public static void main(String[] args) {
int[] sourceInts = {12, 78};
int[] destInts = new int[2];
copyArray(sourceInts, destInts);
12
String[] sourceStrgs = {"Hello ", "there ", "everybody"};
78
String[] destStrgs = new String[3];
copyArray(sourceStrgs, destStrgs);
}
Hello
there
public static void copyArray(Object source, Object dest) {
for (int i = 0; i < Array.getLength(source); i++) {
Array.set(dest, i, Array.get(source, i));
System.out.println(Array.get(dest, i));
}
}
}
everybody
Класс Array
static Object
get(Object array, int index)
Returns the value of the indexed component in the specified array object.
static boolea
n
static byte
getBoolean(Object array, int index)
Returns the value of the indexed component in the specified array object, as a
boolean.
getByte(Object array, int index)
Returns the value of the indexed component in the specified array object, as a byte.
static char
getChar(Object array, int index)
Returns the value of the indexed component in the specified array object, as a char.
static double
getDouble(Object array, int index)
Returns the value of the indexed component in the specified array object, as a double.
static float
getFloat(Object array, int index)
Returns the value of the indexed component in the specified array object, as a float.
static int
getInt(Object array, int index)
Returns the value of the indexed component in the specified array object, as an int.
static int
getLength(Object array)
Returns the length of the specified array object, as an int.
static long
getLong(Object array, int index)
Returns the value of the indexed component in the specified array object, as a long.
static short
getShort(Object array, int index)
Returns the value of the indexed component in the specified array object, as a short
Класс Array
static void
set(Object array, int index, Object value)
Sets the value of the indexed component of the specified array object to the specified new value.
static void
setBoolean(Object array, int index, boolean z)
Sets the value of the indexed component of the specified array object to the specified boolean value.
static void
setByte(Object array, int index, byte b)
Sets the value of the indexed component of the specified array object to the specified byte value.
static void
setChar(Object array, int index, char c)
Sets the value of the indexed component of the specified array object to the specified char value.
static void
setDouble(Object array, int index, double d)
Sets the value of the indexed component of the specified array object to the specified double value.
static void
setFloat(Object array, int index, float f)
Sets the value of the indexed component of the specified array object to the specified float value.
static void
setInt(Object array, int index, int i)
Sets the value of the indexed component of the specified array object to the specified int value.
static void
setLong(Object array, int index, long l)
Sets the value of the indexed component of the specified array object to the specified long value.
static void
setShort(Object array, int index, short s)
Sets the value of the indexed component of the specified array object to the specified short value.
Класс Array
static Objec
newInstance(Class componentType, int length)
t
Creates a new array with the specified component type and length.
static Objec
newInstance(Class componentType, int[] dimensions)
t
Creates a new array with the specified component type and dimensions.
Создание массивов
import java.lang.reflect.*;
class SampleCreateArray {
public static void main(String[] args) {
int[] originalArray = {55, 66};
int[] biggerArray = (int[]) doubleArray(originalArray);
originalArray:
System.out.println("originalArray:");
55
for (int k = 0; k < Array.getLength(originalArray); k++)
66
System.out.println(originalArray[k]);
System.out.println("biggerArray:");
for (int k = 0; k < Array.getLength(biggerArray); k++)
System.out.println(biggerArray[k]);
biggerArray:
55
66
}
0
static Object doubleArray(Object source) {
0
int sourceLength = Array.getLength(source);
Class arrayClass = source.getClass();
Class componentClass = arrayClass.getComponentType();
Object result = Array.newInstance(componentClass,
sourceLength * 2);
System.arraycopy(source, 0, result, 0, sourceLength);
return result;
} }
Создание многомерных
массивов
import java.lang.reflect.*;
class SampleMultiArray {
public static void main(String[] args) {
// The oneDimA and oneDimB objects are one
// dimensional int arrays with 5 elements.
int[] dim1 = {5};
int[] oneDimA = (int[]) Array.newInstance(int.class, dim1);
int[] oneDimB = (int[]) Array.newInstance(int.class, 5);
// The twoDimStr object is a 5 X 10 array of String objects.
int[] dimStr = {5, 10};
String[][] twoDimStr =
(String[][]) Array.newInstance(String.class,dimStr);
// The twoDimA object is an array of 12 int arrays. The tail
// dimension is not defined. It is equivalent to the array
// created as follows:
//
int[][] ints = new int[12][];
int[] dimA = {12};
int[][] twoDimA = (int[][]) Array.newInstance(int[].class, dimA);
}
}
Класс - загрузчик
public abstract class MyClassLoader {
public void initialize() {
public class Do {
}
public static void main(String[] argv) {
/** The work method. The cookie application will call you
System.out.println(“Do");
* here when it is time for you to start cooking.
MyClassLoader loader = null;
*/
String myClassName = argv[0];
public void work() {
try {
}
Class lc = Class.forName(myClassName);
/** The termination method. The cookie application will call you
Object myObject = lc.newInstance();
* here when it is time for you to stop cooking and shut down
loader = (MyClassLoader)myObject;
* in an orderly fashion.
}
} catch (Exception e) {
*/
System.err.println("Error " + myClassName + e);}
public void terminate() {
loader..initialize();
}
loader.work();
public class DemoLoader extends MyClassLoader {
loader.terminate();
}
public void work() {
System.out.println(“Work.");
}
}
public void terminate() {
System.out.println(“Terminate.");
}
}
Javac Do DemoLoader
Тема самостоятельной работы
Написать загрузчик любых классов.
В программе должны
идентифицироваться все методы и
поля загружаемого класса.
