Exercise 21
Exercise 21
QUESTION:
?????????????????
ANSWER:
class Singleton {
private Singleton() {
} v
public void setMessage(String s) {
message=s;
}
public static Singleton createSingleton() {
if(null == instance) {
instance = new Singleton();
}
return instance;
}
public String toString() {
return( getClass().getName() + " [ " + message + " ]");
}
private String message;
private static Singleton instance;
}
class SingletonTest {
public static void main(String args[]) {
Singleton s = Singleton.createSingleton();
s.setMessage("Work fine");
System.out.println( s );
}
}
C:\jdk1.2.1\bin>javac Singleton.java
C:\jdk1.2.1\bin>java SingletonTest
Singleton [ Work fine ]
C:\jdk1.2.1\bin>