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2010-06-01T05:01:00Z

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в 17:44, 31 мая 2010

2010-05-31T17:44:27Z

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== Assignment with objects is a bit tricky. ==



<source lang="java">
class Number {
int i;
}
public class MainClass {
public static void main(String[] args) {
Number n1 = new Number();
Number n2 = new Number();
n1.i = 9;
n2.i = 47;
System.out.println("1: n1.i: " + n1.i + ", n2.i: " + n2.i);
n1 = n2;
System.out.println("2: n1.i: " + n1.i + ", n2.i: " + n2.i);
n1.i = 27;
System.out.println("3: n1.i: " + n1.i + ", n2.i: " + n2.i);
}
}</source>



<pre class=codeResult>1: n1.i: 9, n2.i: 47
2: n1.i: 47, n2.i: 47
3: n1.i: 27, n2.i: 27</pre>

== Class Object ==

<OL><LI>All the classes defined are subclasses by default.</LI><LI>Object is a superclass of every class.</LI><LI>The inheritance happens automatically.</LI><LI>Your classes will inherit members from the class Object.</LI></OL>
MethodPurposetoString()returns a string describing the current objectequals()compares two objectsgetClass()returns a Class that identifies the class of the current object.hashCode()calculates a hashcode for an objectnotify()wakes up a thread associated with the current object.notifyAll()wakes up all threads associated with the current object.wait()causes a thread to wait



<source lang="java">
class Dog{
public Dog(String aType){
}
}
public class MainClass{
public static void main(String[] a){
Dog d = new Dog("a");
Class objectType = d.getClass();
System.out.println(objectType.getName());
}
}</source>



<pre class=codeResult>Dog</pre>

== Demonstrate Run-Time Type Information. ==



<source lang="java">
class X {
int a;
float b;
}
class Y extends X {
double c;
}
class MainClass {
public static void main(String args[]) {
X x = new X();
Y y = new Y();
Class<?> clObj;
clObj = x.getClass();
System.out.println("x is object of type: " + clObj.getName());
clObj = y.getClass();
System.out.println("y is object of type: " + clObj.getName());

clObj = clObj.getSuperclass();
System.out.println("y"s superclass is " + clObj.getName());
}
}</source>



== Getting java.lang.Class: Information about your object ==



<source lang="java">
public class MainClass {
public static void main(String[] a) {
String country = "Canada";
Class myClass = country.getClass();
System.out.println(myClass.getName());
}
}</source>



<pre class=codeResult>java.lang.String</pre>

== Storing a reference to the String object as type Object ==

<p>A variable of type Object can store a reference to an object of any class type.</p>



<source lang="java">
public class MainClass {
public static void main(String[] a) {
String saying = "A stitch in time saves nine.";
Object str = saying;
System.out.println(str);
System.out.println(str.getClass().getName());
}
}</source>



<pre class=codeResult>A stitch in time saves nine.
java.lang.String</pre>

== The "Class" class also brings the possibility of creating an object without using the new keyword. ==

<OL><LI>The static forName method creates a Class object of the given class name.</LI><LI>The newInstance method creates a new instance of a class.</LI></OL>



<source lang="java">
public class MainClass {
public static void main(String[] a) {
Class klass = null;
try {
klass = Class.forName("java.lang.String");
} catch (ClassNotFoundException e) {

}

if (klass != null) {
try {
// create an instance of the Test class
String test = (String) klass.newInstance();

} catch (IllegalAccessException e) {
} catch (InstantiationException e) {
}
}
}
}</source>

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Admin: 1 версия

в 17:44, 31 мая 2010