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OCAJP7 part 3 - from book

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Quiz by . ., updated more than 1 year ago
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Created by . . almost 8 years ago
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Resource summary

Question 1

Question
Only public and protected constructors are inherited from super class if the subclass is not in the same package.
Answer
  • True
  • False

Question 2

Question
Which constructor is valid in class BlaBla
Answer
  • BlaBla(BlaBla a)
  • private BlaBla()
  • public final BlaBla(int i)
  • public static BlaBla(char o)

Question 3

Question
Given the following code, which of these constructors can be added to class B without causing a compile time error? class A{ int i; public A(int x) { this.i = x; } } class B extends A{ int j; public B(int x, int y) { super(x); this.j = y; } }
Answer
  • B( ) { }
  • B(int y ) { j = y; }
  • B(int y ) { super(y*2 ); j = y; }
  • B(int y ) { i = y; j = y*2; }
  • B(int z ) { this(z, z); }

Question 4

Question
Consider the following array definitions: int[] array1, array2[]; int[][] array3; int[] array4[], array5[]; Which of the following are valid statements?
Answer
  • array2 = array3;
  • array2 = array4;
  • array1 = array2;
  • array4 = array1;
  • array5 = array3

Question 5

Question
What will be the result of trying to compile and execute of the following program? public class TestClass{ public static void main(String args[] ){ int i = 0 ; int[] iA = {10, 20} ; iA[i] = i = 30 ; System.out.println(""+ iA[ 0 ] + " " + iA[ 1 ] + " "+i) ; } }
Answer
  • It will throw ArrayIndexOutofBoundsException at Runtime.
  • Compile time Error.
  • It will prints 10 20 30
  • It will prints 30 20 30
  • It will prints 0 20 30

Question 6

Question
What will the following program print? class Test{ public static void main(String[] args){ int i = 4; int ia[][][] = new int[i][i = 3][i]; System.out.println( ia.length + ", " + ia[0].length+", "+ ia[0][0].length); } }
Answer
  • It will not compile.
  • 3, 4, 3
  • 3, 3, 3
  • 4, 3, 4
  • 4, 3, 3

Question 7

Question
Consider the following program... class ArrayTest{ public static void main(String[] args){ int ia[][] = { {1, 2}, null }; for (int i = 0; i < 2; i++) for (int j = 0; j < 2; j++) System.out.println(ia[i][j]); } } Which of the following statements are true?
Answer
  • It will not compile.
  • It will throw an ArrayIndexOutOfBoundsException at Runtime.
  • It will throw a NullPointerException at Runtime.
  • It will compile and run without throwing any exceptions.
  • None of the above.

Question 8

Question
Consider the following class... class Test{ public static void main(String[ ] args){ int[] a = { 1, 2, 3, 4 }; int[] b = { 2, 3, 1, 0 }; System.out.println( a [ (a = b)[3] ] ); } } What will it print when compiled and run ?
Answer
  • It will not compile.
  • It will throw ArrayIndexOutOfBoundsException when run.
  • It will print 1.
  • It will print 3.
  • It will print 4
  • It will print 0

Question 9

Question
Given the following program, which statements are true? // Filename: TestClass.java public class TestClass{ public static void main(String args[]){ A[] a, a1; B[] b; a = new A[10]; a1 = a; b = new B[20]; a = b; // 1 b = (B[]) a; // 2 b = (B[]) a1; // 3 } } class A { } class B extends A { }
Answer
  • Compile time error at line 3.
  • The program will throw a java.lang.ClassCastException at the line labelled 2 when run.
  • The program will throw a java.lang.ClassCastException at the line labelled 3 when run.
  • The program will compile and run if the (B[ ] ) cast in the line 2 and the whole line 3 is removed.

Question 10

Question
Which of these statements are true?
Answer
  • If a RuntimeException is not caught, the method will terminate and normal execution of the thread will resume.
  • An overriding method must declare that it throws the same exception classes as the method it overrides.
  • The main method of a program can declare that it throws checked exceptions.
  • A method declaring that it throws a certain exception class may throw instances of any subclass of that exception class.
  • finally blocks are executed if and only if an exception gets thrown while inside the corresponding try block.

Question 11

Question
Consider the following code... public class TestClass{ class MyException extends Exception {} public void myMethod() throws XXXX{ throw new MyException(); } } Can we replace XXXX with MyException?
Answer
  • True
  • False

Question 12

Question
What will the following program print? class Test{ public static void main(String[] args){ int i = 4; int ia[][][] = new int[i][i = 3][i]; System.out.println( ia.length + ", " + ia[0].length+", "+ ia[0][0].length); } }
Answer
  • It will not compile.
  • 3, 4, 3
  • 3, 3, 3
  • 4, 3, 4
  • 4, 3, 3

Question 13

Question
What will the following code print ? class Test{ public static void main(String[] args){ int k = 1; int[] a = { 1 }; k += (k = 4) * (k + 2); a[0] += (a[0] = 4) * (a[0] + 2); System.out.println( k + " , " + a[0]); } }
Answer
  • It will not compile.
  • 4 , 4
  • 25 , 25
  • 13 , 13
  • None of the above.

Question 14

Question
What will the following code print when compiled and run? class Base{ void methodA(){ System.out.println("base - MethodA"); } } class Sub extends Base{ public void methodA(){ System.out.println("sub - MethodA"); } public void methodB(){ System.out.println("sub - MethodB"); } public static void main(String args[]){ Base b=new Sub(); //1 b.methodA(); //2 b.methodB(); //3 } }
Answer
  • sub - MethodA and sub - MethodB
  • base - MethodA and sub - MethodB
  • Compile time error at //1
  • Compile time error at //2
  • Compile time error at //3

Question 15

Question
What will be printed? class A1 { static int i; } class A { public static void main(String[] args) { A1 a1 = null; System.out.println(a1.i); } }
Answer
  • 10
  • This code will not compile.
  • NullpointerException will be thrown
  • 0

Question 16

Question
What will be the output of: Short k = 9; Integer i = 9; System.out.println(k == i); Please provide argumentation to your answer.
Answer
  • true
  • false
  • Compilation error
  • Exception in runtime
  • Other

Question 17

Question
Consider the following code: class A{ public XXX m1(int a){ return a*10/4-30; } } class A2 extends A{ public YYY m1(int a){ return a*10/4.0; } } What can be substituted for XXX and YYY so that it can compile without any problems?
Answer
  • int, int
  • int, double
  • double, double
  • double, int
  • Nothing, they are simply not compatible.

Question 18

Question
Consider the following code: class A{ A() { print(); } void print() { System.out.println("A"); } } class B extends A{ int i = Math.round(3.5f); public static void main(String[] args){ A a = new B(); a.print(); } void print() { System.out.println(i); } } What will be the output when class B is run ?
Answer
  • It will print A, 4.
  • It will print A, A
  • It will print 0, 4
  • It will print 4, 4
  • None of the above.

Question 19

Question
Consider : class A { public void perform_work(){} } class B extends A { public void perform_work(){} class C extends B { public void perform_work(){} } } How can you let perform_work() method of A to be called from an instance method in C?
Answer
  • ( (A) this ).perform_work( );
  • super.perform_work( );
  • super.super.perform_work( );
  • this.super.perform_work( );
  • It is not possible.

Question 20

Question
Expression (s instanceof java.util.Date) will return false if 's' was declared as a variable of class java.lang.String .
Answer
  • True
  • False
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