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2010-06-01T06:01:57Z

1 версия

в 18:01, 31 мая 2010

2010-05-31T18:01:43Z

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== Create an object from a string ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
Class[] classParm = null;
Object[] objectParm = null;
try {
String name = "java.lang.String";
Class cl = Class.forName(name);
java.lang.reflect.Constructor co = cl.getConstructor(classParm);
System.out.println(co.newInstance(objectParm));
} catch (Exception e) {
e.printStackTrace();

}
}
}

</source>



== Determine the Superclass of an Object ==



<source lang="java">

import java.util.ArrayList;
public class Main {
public static void main(String[] args) {
System.out.println(new ArrayList().getClass().getSuperclass().getName());
}
}
//java.util.AbstractList

</source>



== Find the Package of an Object ==



<source lang="java">

import java.util.ArrayList;
import java.util.Vector;
public class Main {
public static void main(String[] args) {
System.out.println(new Vector().getClass().getPackage().getName());
System.out.println(new ArrayList().getClass().getPackage().getName());
System.out.println("Test String".getClass().getPackage().getName());
System.out.println(new Integer(1).getClass().getPackage().getName());
}
}
/*
java.util
java.util
java.lang
java.lang
*/

</source>



== For the primitive tipe the interface will be an empty array ==



<source lang="java">

import java.util.Calendar;
import java.util.Date;
public class Main {
public static void main(String[] args) {
Date date = Calendar.getInstance().getTime();

Class c = char.class;
Class[] interfaces = c.getInterfaces();
for (Class intf : interfaces) {
System.out.println("Interface Name = " + intf.getName());
}
}
}

</source>



== Get the class By way of an object ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
Object object = new String();
// By way of an object
Class cls = object.getClass();
}
}

</source>



== Get the fully-qualified name of a class ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
Class cls = java.lang.String.class;
String name = cls.getName();
System.out.println(name);
}
}

</source>



== Get the fully-qualified name of a inner class ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
Class cls = java.util.Map.Entry.class;
String name = cls.getName();
System.out.println(name);
}
}

</source>



== Get the name of an array ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
String name = boolean[].class.getName();
System.out.println(name);
name = byte[].class.getName();
System.out.println(name);
name = char[].class.getName();
System.out.println(name);
name = short[].class.getName();
System.out.println(name);
name = int[].class.getName();
System.out.println(name);
name = long[].class.getName();
System.out.println(name);
name = float[].class.getName();
System.out.println(name);
name = double[].class.getName();
System.out.println(name);
name = String[].class.getName();
System.out.println(name);
name = int[][].class.getName();
System.out.println(name);
}
}

</source>



== Get the name of a primitive type ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
String name = int.class.getName(); // int
System.out.println(name);
}
}

</source>



== Get the name of void ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
Class cls = Void.TYPE;
String name = cls.getName(); // void
}
}

</source>



== Get the unqualified name of a class ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
Class cls = java.util.Map.Entry.class;
String name = cls.getName();
if (name.lastIndexOf(".") > 0) {
name = name.substring(name.lastIndexOf(".") + 1); // Map$Entry
name = name.replace("$", "."); // Map.Entry
}
}
}

</source>



== Getting the Superclass of a Class Object ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
Class cls = java.lang.String.class;
Class sup = cls.getSuperclass(); // java.lang.Object
cls = java.lang.Object.class;
sup = cls.getSuperclass(); // null
}
}

</source>



== If a class object is an interface or a class ==



<source lang="java">

public class Main {
public static void main(String[] args) {
// Checking whether Cloneable is an interface or class
Class clazz = Cloneable.class;
boolean isInterface = clazz.isInterface();
System.out.println("Is Interface = " + isInterface);
}
}

</source>



== Instantiate unknown class at runtime and call the object"s methods ==



<source lang="java">

import java.lang.reflect.Method;
public class Main {
public static void main(String[] args) throws Exception {
Class myclass = Class.forName("java.lang.String");
Method[] methods = myclass.getMethods();
//Object object = myclass.newInstance();
for (int i = 0; i < methods.length; i++) {
System.out.println(methods[i].getName());
//System.out.println(methods[i].invoke(object));
}
}
}
/*
hashCode
compareTo
compareTo
indexOf
indexOf
indexOf
indexOf
equals
toString
charAt
codePointAt
codePointBefore
codePointCount
compareToIgnoreCase
concat
contains
contentEquals
contentEquals
copyValueOf
copyValueOf
endsWith
equalsIgnoreCase
format
format
getBytes
getBytes
getBytes
getBytes
getChars
intern
isEmpty
lastIndexOf
lastIndexOf
lastIndexOf
lastIndexOf
length
matches
offsetByCodePoints
regionMatches
regionMatches
replace
replace
replaceAll
replaceFirst
split
split
startsWith
startsWith
subSequence
substring
substring
toCharArray
toLowerCase
toLowerCase
toUpperCase
toUpperCase
trim
valueOf
valueOf
valueOf
valueOf
valueOf
valueOf
valueOf
valueOf
valueOf
getClass
wait
wait
wait
notify
notifyAll
*/

</source>



== Obtain from where a Class is loaded ==



<source lang="java">

public class Main {
public static void main(String args[]) {
Main m = new Main();
System.out.println(m.getClass().getName() + " is loaded from "
+ m.getClass().getProtectionDomain().getCodeSource().getLocation());
}
}

</source>



== Using Reflection to browse a java class ==



<source lang="java">

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
public class Main {
public static void main(String argv[]) throws Exception{
String className = "String";
Class c = Class.forName(className);
Constructor cst[] = c.getDeclaredConstructors();
// get fields from the Class object
Field f[] = c.getDeclaredFields();
// get methods from the Class object
Method m[] = c.getDeclaredMethods();
// filling the constructors list box
for (int i = 0; i < cst.length; i++) {
System.out.println(cst[i].getName());
}
// filling the fields list box
for (int i = 0; i < f.length; i++) {
System.out.println(f[i].getName());
}
// filling the methods list box
for (int i = 0; i < m.length; i++) {
System.out.println(m[i].getName());
}
}
}

</source>

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Admin: 1 версия

в 18:01, 31 мая 2010