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2010-06-01T06:47:18Z

1 версия

в 18:01, 31 мая 2010

2010-05-31T18:01:45Z

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== Finding Out of what Class an Object is Instantiated ==



<source lang="java">

import java.util.ArrayList;
import java.util.Vector;
public class Main {
public static void main(String[] args) {
Object testObject = new Vector();
if (testObject instanceof Vector)
System.out.println("Object was an instance of the class java.util.Vector");
else if (testObject instanceof ArrayList)
System.out.println("Object was an instance of the class java.util.ArrayList");
else
System.out.println("Object was an instance of the " + testObject.getClass());
}
}
//Object was an instance of the class java.util.Vector

</source>



== Get a class of an object ==



<source lang="java">

import java.util.ArrayList;
import java.util.List;
public class Main {
public static void main(String[] args) {
Person p = new Person("A");
Animal a = new Animal("B");
Thing t = new Thing("C");
String text = "hello";
Integer number = 1000;
List<Object> list = new ArrayList<Object>();
list.add(p);
list.add(a);
list.add(t);
list.add(text);
list.add(number);
for (int i = 0; i < list.size(); i++) {
Object o = list.get(i);
if (o instanceof Person) {
System.out.println("My name is " + ((Person) o).getName());
} else if (o instanceof Animal) {
System.out.println("I live in " + ((Animal) o).getHabitat());
} else if (o instanceof Thing) {
System.out.println("My color is " + ((Thing) o).getColor());
} else if (o instanceof String) {
System.out.println("My text is " + o.toString());
} else if (o instanceof Integer) {
System.out.println("My value is " + ((Integer) o));
}
}
}
}
class Person {
private String name;
public Person(String name) {
this.name = name;
}
public String getName() {
return name;
}
}
class Animal {
private String habitat;
public Animal(String habitat) {
this.habitat = habitat;
}
public String getHabitat() {
return habitat;
}
}
class Thing {
private String color;
public Thing(String color) {
this.color = color;
}
public String getColor() {
return color;
}
}

</source>



== The difference between instanceof and class ==



<source lang="java">

// : c10:FamilyVsExactType.java
// The difference between instanceof and class
// From "Thinking in Java, 3rd ed." (c) Bruce Eckel 2002
// www.BruceEckel.ru. See copyright notice in CopyRight.txt.
class Base {
}
class Derived extends Base {
}
public class FamilyVsExactType {
static void test(Object x) {
System.out.println("Testing x of type " + x.getClass());
System.out.println("x instanceof Base " + (x instanceof Base));
System.out.println("x instanceof Derived " + (x instanceof Derived));
System.out.println("Base.isInstance(x) " + Base.class.isInstance(x));
System.out.println("Derived.isInstance(x) "
+ Derived.class.isInstance(x));
System.out.println("x.getClass() == Base.class "
+ (x.getClass() == Base.class));
System.out.println("x.getClass() == Derived.class "
+ (x.getClass() == Derived.class));
System.out.println("x.getClass().equals(Base.class)) "
+ (x.getClass().equals(Base.class)));
System.out.println("x.getClass().equals(Derived.class)) "
+ (x.getClass().equals(Derived.class)));
}
public static void main(String[] args) {
test(new Base());
test(new Derived());
}
} ///:~

</source>

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Admin: 1 версия

в 18:01, 31 мая 2010