import java.util.Random; public class Rando...

Dynamic proxy can be used to eliminate the need to stub out unused interface methods. This is an example for a simple SAX content handler for XML parsing. The org.xml.sax.ContentHandler interface requires 11 methods be implemented but we only need three: import java.io.IOException; import java.util.Ar... With a dynamic proxy, we don't need the empty blocks for the unused methods: import java.io.IOException; import java.util.Ar... Equivalently (with anonymous inner class): import java.io.IOException; import java.util.Ar... demo.xml : <breakfast-menu> <food> <name>Belgian W...

import java.util.Arrays; public class Array...

Facts: Dynamic proxy classes are generated by the Java runtime, from a list of interfaces given by the user. The generated proxy class implements all interfaces given by the user. The dynamic proxy class is not synthetic . The dynamic proxy class is useless without a user supplied InvocationHandler class, since there's only one constructor for the proxy class and it takes a InvocationHandler as parameter. Example code: import java.lang.reflect.Constructor; import ja... Output: Class: $Proxy0 isSynthetic: false Constructo...

While doing some Java reflection code, I noticed the method Class.isSynthetic() , which the JavaDoc says returns " true if and only if this class is a synthetic class as defined by the Java Language Specification". However, there's no definition of "synthetic class" in the JLS ! The only thing that I can find that remotely resembles a definition is in the JVM spec , where it defines the synthetic attribute : "The Synthetic attribute is a fixed-length attribute in the attributes table of ClassFile (§4.1), field_info (§4.5), and method_info (§4.6) structures. A class member that does not appear in the source code must be marked using a Synthetic attribute." By this definition, a default constructor, which does not appear in the source code, should...

Given a class A : class A { public int doWork(String s, int i... it is OK to call method doWork with both primitive types and the corresponding wrapping object types: new A().doWork("Hello", 1, false); new A().doWo... However, if you find method by parameter types with Java reflection, the types must match exactly, i.e., Class<?> c = Class.forName("A"); // This call f... This is a utility to find methods with compatible parameter types: import java.lang.reflect.*; import java.util.*;... Example usage: Method m = ReflectionUtil.getCompatibleMethod(c, "...

This may be helpful in debugging reflection code. import java.lang.reflect.Modifier; public c...

Some javap usage examples. Start from HelloWorld.java : @Deprecated public class HelloWorld { pu... javap -c HelloWorld outputs: Compiled from "HelloWorld.java" public class He... javap -v HelloWorld outputs ( -v for verbose mode): Compiled from "HelloWorld.java" public class He... The output consists of: " Compiled from... " header Class attributes. For the HelloWorld example, there are two: SourceFile and Deprecated . Minor and major class file version Constant pool Disassembled code LineNumberTable for debugging purposes. javap by default only prints package/protected/public members. To display all members including private, use the -p switch. javap -v -p HelloWorld

Code: public class SplitTest { public static void... Output: Split 1: 'a' ' b ' ' c ' 'd ' S...

Create BroadcastReceiver class (implement onReceive ): import android.content.*; import android.net.Ur... Declare receiver with intent filter in AndroidManifest.xml : <receiver android:name="PackageChangeReceiver"> ... In order to receive the broadcasts, the data element is required in addition to the action elements in the intent filter. When a package is being replaced, the Android system actually broadcasts three intents (in this order): ACTION_PACKAGE_REMOVED ACTION_PACKAGE_ADDED ACTION_PACKAGE_REPLACED To tell that that an ACTION_PACKAGE_REMOVED or ACTION_PACKAGE_ADDED intent is received as the result of a package being replaced (instead of plain add or remove), check the EXTRA_REPLACING flag: boolean replacing = intent.getBooleanExtra(Intent....