Monday, February 6, 2012

SCJP model question answer page 6


51)
Which of the following methods are static members of the Thread class?

join

run

sleep

start

wait

Ans: 3


52)
class C {
public static void main(String[] args) {
  try
    {
        int i1=3/0;
    }
    System.out.println("hai");
    catch(NullpointerException e)
    {
     }
    finally
    {
              System.out.println("finally);
    }
}
}

compile time errors

print hai and finally

the code compiles and runs fine

none of the above

Ans: 1


53)
class c1
{
            public static void main(String a[])
            {
                System.out.println(Double.NaN==Double.NaN);
                System.out.println(Double.NaN!=Double.NaN);
                System.out.println(Float.NaN==Double.NaN);
            }
}


prints false true false

print true false true

prints true true true

prints false false false

compiletime error

Ans: 1


54)
class C {
  public static void main ( String ka [ ] )
            {
                      Thread t = Thread . currentThread ( ) ;
                      t . setPriority ( - 1 ) ;
                      System . out . println ( " Done ! " ) ;
             }
};


compile time error

Runtime Exception

The code compiles and runs fine

None of the above

Ans: 2


55)
class c1
{
   public void m1()
    {
       System.out.println("m1 method in C1 class");
     }
}
class c2
{
  public c1 m1()
   {
     return new c1(){
       public void m1()
          {
              System.out.println("m1 mehod in anonymous class");
          }
};
}
public static void main(String a[])
 {
        c1 ob1 =new c2().m1();
        ob1.m1();
}
}

prints m1 method in C1 class

prints m1 method in anonumous class

compile time error

Runtime error

none of the above

Explanation:
the anonymous class overrides the m1 method in c1.so according to the dynamic dispatch the m1 method in the anonymous is called
Ans: 2


56)
class c1 extends Exception
{
}
class c2
{
   static void m1()
    {
       throw new c1();
     }
  public static void main(String a[])
   {
         
    }
}


compile time error

Runtime Exception

The code compiles and runs fine

None of the above

Ans: 1


57)
class C {
            static void m1(Object x) {System.out.print("Object");}
            static void m1(String x) {System.out.print("String");}
            public static void main(String[] args) {
            m1(null);
            }
}

Prints Object

Prints String

compiletime error

None of the above

Explanation:
The more specific of the two, m(String x), is chosen
Ans: 2


58)
all classes of the java.lang package are automatically imported

true

false

Ans: 1

59)
The constructor for the Math class is private, so it cannot be instaniated

true

false

Ans: 1


60)
class C {
public static void main(String[] args) {
 int x=2;
 int y=3;
   if((y==x++)|(x<++y)){                    
         System.out.println(x+""+y);
        }
}}

prints  34

prints  33

compile time error

Runtime exception

None of the above

Ans: 1

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