question 2

Question 1)

What will happen when you attempt to compile and run this code?

abstract class Base{ abstract public void myfunc(); public void another(){ System.out.println("Another method"); }}

public class Abs extends Base{ public static void main(String argv[]){ Abs a = new Abs(); a.amethod(); } public void myfunc(){ System.out.println("My func"); }

public void amethod(){ myfunc(); }}

1) The code will compile and run, printing out the words "My Func"2) The compiler will complain that the Base class has non abstract methods3) The code will compile but complain at run time that the Base class has non abstract methods4) The compiler will complain that the method myfunc in the base class has no body, nobody at all to looove it

Question 2)


public class MyMain{public static void main(String argv){ System.out.println("Hello cruel world"); }}

1) The compiler will complain that main is a reserved word and cannot be used for a class2) The code will compile and when run will print out "Hello cruel world"3) The code will compile but will complain at run time that no constructor is defined4) The code will compile but will complain at run time that main is not correctly defined

Question 3)

Which of the following are Java modifiers?

1) public2) private3) friendly4) transient

Question 4)


class Base{ abstract public void myfunc(); public void another(){ System.out.println("Another method"); }}

public class Abs extends Base{ public static void main(String argv[]){ Abs a = new Abs(); a.amethod(); } public void myfunc(){ System.out.println("My func"); } public void amethod(){ myfunc(); }

}

1) The code will compile and run, printing out the words "My Func"2) The compiler will complain that the Base class is not declared as abstract.3) The code will compile but complain at run time that the Base class has non abstract methods4) The compiler will complain that the method myfunc in the base class has no body, nobody at all to looove it

Question 5)

Why might you define a method as native?

1) To get to access hardware that Java does not know about2) To define a new data type such as an unsigned integer3) To write optimised code for performance in a language such as C/C++4) To overcome the limitation of the private scope of a method

Question 6)


class Base{public final void amethod(){ System.out.println("amethod"); }}

public class Fin extends Base{public static void main(String argv[]){ Base b = new Base(); b.amethod(); }}

1) Compile time errror indicating that a class with any final methods must be declared final itself2) Compile time error indicating that you cannot inherit from a class with final methods

3) Run time error indicating that Base is not defined as final4) Success in compilation and output of "amethod" at run time.

Question 7)


public class Mod{public static void main(String argv[]){} public static native void amethod();}

1) Error at compilation: native method cannot be static2) Error at compilation native method must return value3) Compilation but error at run time unless you have made code containing native amethod available4) Compilation and execution without error

Question 8)


private class Base{}

public class Vis{

transient int iVal;

public static void main(String elephant[]){

}

}

1) Compile time error: Base cannot be private2) Compile time error indicating that an integer cannot be transient3) Compile time error transient not a data type4) Compile time error malformed main method

Question 9)

What happens when you attempt to compile and run these two files in the same directory?

//File P1.java

package MyPackage;

class P1{

void afancymethod(){

System.out.println("What a fancy method");

}

}

//File P2.java

public class P2 extends P1{

afancymethod();

}

1) Both compile and P2 outputs "What a fancy method" when run2) Neither will compile3) Both compile but P2 has an error at run time4) P1 compiles cleanly but P2 has an error at compile time

Question 10)

Which of the following are legal declarations?

1) public protected amethod(int i)2) public void amethod(int i)3) public void amethod(void)4) void public amethod(int i)

Answers

Answer 1)

1) The code will compile and run, printing out the words "My Func"

An abstract class can have non abstract methods, but any class that extends it must implement all of the abstract methods.

Answer 2)

4) The code will compile but will complain at run time that main is not correctly defined

The signature of main has a parameter of String rather than string array

Answer 3)

1) public2) private4) transient

Although some texts use the word friendly when referring to visibility it is not a Java reserved word. Note that the exam will almost certainly contain questions that ask you to identify Java keywords from a list

Answer 4)

2) The compiler will complain that the Base class is not declared as abstract.

The actual error message using my JDK 1.1 compiler was

Abs.java:1: class Base must be declared abstract.

It does not define void myfunc

() from class Base.

class Base{

^

1 error

Answer 5)

1) To get to access hardware that Java does not know about3) To write optimised code for performance in a language such as C/C++

Although the creation of "Pure Java" code is highly desirable, particularly to allow for platform independence, it should not be a religion, and there are times when native code is required.

Answer 6)

4) Success in compilation and output of "amethod" at run time.

This code calls the version of amethod in the Base class. If you were to attempt to implement an overriden version of amethod in Fin you would get a compile time error.

Answer 7)

4) Compilation and execution without error

There is no call to the native method and so no error occurs at run time

Answer 8)

1) Compile time error: Base cannot be private

A top level class such as base cannot be declared to be private.

Answer 9)

4) P1 compiles cleanly but P2 has an error at compile time

Even though P2 is in the same directory as P1, because P1 was declared with the package statement it is not visible from P2

Answer 10)

2) public void amethod(int i)

If you thought that option 3 was legal with a parameter argument of void you may have to empty some of the C/C++ out of your head.Option 4) is not legal because method return type must come immediatly before the method name.

Question 1)

Given the following code

public class FinAc{ static int l = 4; private int k=2;public static void main(String argv[]){ FinAc a = new FinAc(); a.amethod(); } public void amethod(){ final int i = 99; int j = 6; class CInMet{ public void mymethod(int q){ //Here }//end of mymethod }//End of CInMet CInMet c = new CInMet(); c.mymethod(i); }//End of amthod}

Which of the following variables are visible on the line marked with the comment //Here?

1) l2) k3) i4) j

Question 2)

Which of the following will compile correctly?

1)

//A Commentimport java.awt.*;class Base{};

2)

import java.awt.*;package Spot;class Base();

3)

//Another commentpackage myprogs.MyPack;public class MyPack{}

4)

class Base{}import java.awt.*;public class Tiny{}

Question 3)

Which of the following statements are true?

1) An inner class may be defined as static2) An inner class may NOT be define as private3) An anonymous class may have only one constructor4) An inner class may extend another class

Question 4)

From code that has no current this reference how can you create an instance of an inner class?

1) Outer.Inner i = new Outer().new Inner(); 2) Without a this reference an inner class cannot be created3) Outer.Inner i = Outer().new new Inner();4) Outer i = Outer.new().Inner();

Answers

Answer 1)

1) l2) k3) iA class defined within a method can only see final fields from its enclosing method. However it can see the fields in its enclosing class including private fields. The field j was not defined as final.

Answer 2)

1)

//A Commentimport java.awt.*;class Base{};

3)

//Another commentpackage myprogs.MyPack;public class MyPack{}

Any package statement must be the first item in a file (apart from comments). An import statement must come after any package statement and before any code.

Answer 3)

1) An inner class may be defined as static4) An inner class may extend another class

How could an anonymous class have a constructor? Inner classes may be defined as private.

Answer 4)

1) Outer.Inner i = new Outer().new Inner();

Questions

Question 1)

Which of the following are collection classes?

1) Collection2) Iterator3) HashSet4) Vector

Question 2)

Which of the following are true about the Collection interface?

1) The Vector class has been modified to implement Collection2) The Collection interface offers individual methods and Bulk methods such as addAll3) The Collection interface is backwardly compatible and all methods are available within the JDK 1.1 classes4) The collection classes make it unnecessary to use arrays

Question 3)

Which of the following are true?

1) The Set interface is designed to ensure that implementing classes have unique members2) Classes that implement the List interface may not contain duplicate elements3) The Set interface is designed for storing records returned from a database query4) The Map Interface is not part of the Collection Framework

Question 4)

Which of the following are true?

1) The elements of a Collection class can be ordered by using the sort method of the Collection interface2) You can create an ordered Collection by instantiating a class that implements the List interface3) The Collection interface sort method takes parameters of A or D to change the sort order, Ascending/Descending4) The elements of a Collection class can be ordered by using the order method of the Collection interface

Question 5)

You wish to store a small amount of data and make it available for rapid access. You do not have a need for the data to be sorted, uniqueness is not an issue and the data will remain fairly static Which data structure might be most suitable for this requirement?

1) TreeSet2) HashMap3) LinkedList4) an array

Question 6)

Which of the following are Collection classes?

1) ListBag2) HashMap3) Vector4) SetList

Question 7)

How can you remove an element from a Vector?

1) delete method2) cancel method3) clear method4) remove method

Answers

Answer 1)

3) HashSet4) Vector

The other two are Interfaces not classes

Answer 2)

1) The Vector class has been modified to implement Collection2) The Collection interface offers individual methods and Bulk methods such as addAll

The Collection classes are new to the JDK1.2 (Java2) release. With the exception of the classes that have been retrofitted such as Vector and BitSet the, if you run any of the Collections through an older JDK you will get a compile time error.

Answer 3)

1) The Set interface is designed to ensure that implementing classes have unique members

Elements of a class that implements the List interface may contain duplicate elements. Although a class that implements the Set interface might be used for storing records returned from a database query, it is not designed particularly for that purpose.

Answer 4)

2) You can create an ordered Collection by instantiating a class that implements the List interface

Answer 5)

4) an array

For such a simple requirement an ordinary array will probably be the best solution

Answer 6)

2) HashMap3) Vector

With the release of JDK 1.2 (Java2) the Vector class was "retro-fitted" to become a member of the Collection Framework

Answer 7)

4) remove method

question 2

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