if(obj instanceof Dog) {
  Dog d = (Dog)obj;
  d.bark();
}

// with reflection
Class <!--?--> c = Class.forName("classpath.and.classname");
Object dog = c.newInstance();
 
Method m = c.getDeclaredMethod("bark", new Class<!--?-->[0]);
m.invoke(dog);

<bean class="com.programcreek.Foo" id="someID">
<property name="someField" value="someValue">
</property></bean>

<code><code><code><code><code><code><servlet>
<servlet name="">someServlet 
<servlet>com.programcreek.WhyReflectionServlet</servlet>
<servlet data-filtered="filtered"></servlet></servlet></servlet></code></code></code></code></code></code>

package com.longluo.java.interview.reflection;
 
public class ReflectionHelloWorld {
 
  public static void main(String[] args) {
    Foo f = new Foo();
    System.out.println(f.getClass().getName());
  }
}
 
class Foo {
  public void print() {
    System.out.println("abc");
  }
}

com.longluo.java.interview.reflection.Foo

package com.longluo.java.interview.reflection;
 
import java.lang.reflect.Method;
 
public class ReflectionHelloWorld {
 
  /*
   * public static void main(String[] args) { Foo f = new Foo();
   * System.out.println(f.getClass().getName()); }
   */
 
  public static void main(String[] args) {
    Foo f = new Foo();
    Method method;
    try {
      method = f.getClass().getMethod("print", new Class<!--?-->[0]);
      method.invoke(f);
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
 
}
 
class Foo {
  public void print() {
    System.out.println("abc");
  }
}

abc

package com.longluo.java.interview.reflection;
 
import java.lang.reflect.Method;
 
public class ReflectionHelloWorld {
 
  public static void main(String[] args) {
    // create instance of "Class"
 
    Class<!--?--> c = null;
 
    try {
      c = Class.forName("com.longluo.java.interview.reflection.Foo");
 
    } catch (Exception e) {
      e.printStackTrace();
    }
 
    // create instance of "Foo"
    Foo f = null;
    try {
      f = (Foo) c.newInstance();
    } catch (Exception e) {
      e.printStackTrace();
    }
    f.print();
  }
 
}
 
class Foo {
  public void print() {
    System.out.println("abc");
  }
}

package com.longluo.java.interview.reflection;
import java.lang.reflect.Constructor;
public class ReflectionHelloWorld4 {
  public static void main(String[] args) {
    // create instance of "Class"
    Class<!--?--> c = null;
    try {
      c = Class.forName("com.longluo.java.interview.reflection.Foo4");
    } catch (Exception e) {
      e.printStackTrace();
    }
    // create instance of "Foo"
    Foo4 f1 = null;
    Foo4 f2 = null;
    // get all constructors
    Constructor<!--?--> cons[] = c.getConstructors();
    try {
      f1 = (Foo4) cons[0].newInstance();
      f2 = (Foo4) cons[1].newInstance("abc");
    } catch (Exception e) {
      e.printStackTrace();
    }
    f1.print();
    f2.print();
  }
}
class Foo4 {
  String s;
  public Foo4() {
  }
  public Foo4(String s) {
    this.s = s;
  }
  public void print() {
    System.out.println(s);
  }
}

null
abc

package com.longluo.java.interview.reflection;
import java.lang.reflect.Array;
public class ReflectionHelloWorld5 {
  public static void main(String[] args) {
    int[] intArray = { 1, 2, 3, 4, 5 };
    int[] newIntArray = (int[]) changeArraySize(intArray, 10);
    print(newIntArray);
    String[] atr = { "a", "b", "c", "d", "e" };
    String[] str1 = (String[]) changeArraySize(atr, 10);
    print(str1);
  }
  // change array size
  public static Object changeArraySize(Object obj, int len) {
    Class<!--?--> arr = obj.getClass().getComponentType();
    Object newArray = Array.newInstance(arr, len);
    // do array copy
    int co = Array.getLength(obj);
    System.arraycopy(obj, 0, newArray, 0, co);
    return newArray;
  }
  // print
  public static void print(Object obj) {
    Class<!--?--> c = obj.getClass();
    if (!c.isArray()) {
      return;
    }
    System.out.println("\nArray length:" + Array.getLength(obj));
    for (int i = 0; i < Array.getLength(obj); i++) {
      System.out.print(Array.get(obj, i) + " ");
    }
  }
}

Array length:10
1 2 3 4 5 0 0 0 0 0
Array length:10
a b c d e null null null null null