Certified Java Programmer Mock Exam

Question 1

A class can not be called "tightly encapsulated" unless which of the following is true?

Question 2

Which of the following instance methods should only be called by a thread that holds the lock of the instance on which the method is invoked?

Question 3

Which of these methods is a static member of the java.lang.String class?

Question 4

class SRC107 {
  public static void main (String[] args) {
    int a = -1; long b = -2;
    float c = -3.0f; double d = -4.0;
    a = Math.abs(a); b = Math.abs(b);
    c = Math.abs(c); d = Math.abs(d);
    System.out.print(a+b+c+d);
}}

What is the result of attempting to compile and run the program?

Question 5

class MWC205 {
  static void m1(StringBuffer s1) {
    s1.append("B"); System.out.print(s1);
  }
  static void m2(StringBuffer s1) {
    s1 = new StringBuffer("C"); System.out.print(s1);
  }
  public static void main(String[] s) {
    StringBuffer s1 = new StringBuffer("A");
    m1(s1); m2(s1);
    System.out.print(s1);
}}

What is the result of attempting to compile and run the program?

Question 6

class F {
  public static void main (String[] args) {
    System.out.print(Byte.MIN_VALUE+","+Byte.MAX_VALUE);
}}

What is the result of attempting to compile and run the program?

Question 7

class D {
  public static void main (String args[]) {
    boolean b1 = Integer.MIN_VALUE == 0x80000000;
    boolean b2 = Integer.MAX_VALUE == 0x7FFFFFFF;
    System.out.print(b1 + "," + b2);
}}

What is the result of attempting to compile and run the program?

Question 8

class G {
  public static void main (String[] args) {
    Long l1 = new Long("1"), l2 = new Long("1");
    int h1 = l1.hashCode(), h2 = l2.hashCode();
    StringBuffer s1 = new StringBuffer("1");
    StringBuffer s2 = new StringBuffer("1");
    int h3 = s1.hashCode(), h4 = s2.hashCode();
    System.out.print((l1.equals(l2) & (h1==h2)) + ",");
    System.out.print(s1.equals(s2) | (h3==h4));
}}

What is the result of attempting to compile and run the program?

Question 9

Which methods of the java.lang.Double class return a primitive value?

Question 10

class E {
  static String m1(boolean b) {return "b";}
  static String m1(Boolean b) {return "B";}
  public static void main(String[] args) {
    Boolean b1 = new Boolean(true);
    System.out.print(m1(Boolean.valueOf(null)));
    System.out.print(m1(b1.booleanValue()));
    System.out.println(m1(Boolean.TRUE));
}}

What is the result of attempting to compile and run the program?

Question 11

class F {
  static String m(float f) {return "f";}
  static String m(Float f) {return "F";}
  public static void main (String[] args) {
    Float f1 = new Float(1);
    System.out.print(m(f1.parseFloat("1")));
    System.out.print(m(f1.floatValue()));
    System.out.print(m(f1.valueOf("1")));
}}

What is the result of attempting to compile and run the program?

Question 12

Which interface of the java.util package offers the specified behavior?

Question 13

import java.util.*;
class GFC105 {
  public static void main (String args[]) {
    Object a = new HashSet(), b = new HashMap();
    Object c = new Hashtable();
    System.out.print((a instanceof Collection)+",");
    System.out.print((b instanceof Collection)+",");
    System.out.print(c instanceof Collection);
}}

What is the result of attempting to compile and run the program?

Question 14

class B {
  private int i1;
  public int hashCode() {return 1;}
}
class C {
  private int i1;
  public int hashCode() {return -1;}
}
class D {
  private int i1;
  public int hashCode() {return i1;}
}

Suppose that the equals method of classes B, C and D all make use of the value of the int variable, i1. Which class has a hashCode method that is not consistent with the hash code contract?

Question 15

class JSC103 {
  transient float e = 1;         // 1
  volatile float f = 1;          // 2
  abstract float j = 1;          // 3
  final float g = 1;             // 4
  private final float k = 1;     // 5
  private transient float l = 1; // 6
  volatile final float m = 1;    // 7
}

Compile-time errors are generated at which lines?

Question 16

Which of the following statements are true?

Question 17

protected class D {}    // 1
synchronized class F {} // 2
volatile class H {}     // 3
final class B {}        // 4

Suppose these are top-level class declarations and not nested class declarations. Which of these declarations would not produce a compile-time error?

Question 18

class Z {
  static class F {}       // 1
  synchronized class G {} // 2
  transient class H {}    // 3
  volatile class I {}     // 4
}

Which class declaration does not result in a compile-time error?

Question 19

class Level1Exception extends Exception {}
class Level2Exception extends Level1Exception {}
class Level3Exception extends Level2Exception {}
class Purple {
  public static void main(String args[]) {
    int a,b,c,d,f,g,x;
    a = b = c = d = f = g = 0;
    x = 5;
    try {
      try {
	switch (x) {
          case 1: throw new Level1Exception();
          case 2: throw new Level2Exception();
          case 3: throw new Level3Exception();
          case 4: throw new Exception();
      } a++; }
      catch (Level2Exception e) {b++;}
      finally {c++;}
    }
    catch (Level1Exception e) { d++;}
    catch (Exception e) {f++;}
    finally {g++;}
    System.out.print(a+","+b+","+c+","+d+","+f+","+g);
}}

What is the result of attempting to compile and run the program?

Question 20

class GFC202 {}
class GFC203 extends GFC202 {}
class GFC204 {
  static void m(GFC202 x) {System.out.print("GFC202");}
  static void m(GFC203 x) {System.out.print("GFC203");}
  public static void main(String[] args) {
    m(null);
}}

What is the result of attempting to compile and run the program?

Question 21

class T {
  private int i1, i2;
  void printI1I2() {System.out.print("T, i1="+i1+", i2="+i2);}
  T(int i1, int i2) {
    this.i1=i1; this.i2=i2;
}}
class U extends T {
  private int i1, i2;
  void printI1I2() {System.out.print("U, i1="+i1+", i2="+i2);}
  U(int i1, int i2) {this.i1=i1; this.i2=i2;}
  public static void main(String[] args) {
    T t = new U(1,2); t.printI1I2();
}}

What is the result of attempting to compile and run the program?

Question 22

class F {
  public void m1() {Z.m1();}      // 1
  private static class Y {
    private static void m1() {
      System.out.print("Y.m1 ");
  }}
  private static class Z {
    private static void m1(){
      System.out.print("Z.m1 ");
      Y.m1();                     // 2
  }}
  public static void main(String[] args) {
    new F().m1();
}}

What is the result of attempting to compile and run the program?

Question 23

class A {void m1(A a) {System.out.print("A");}}
class B extends A {void m1(B b) {System.out.print("B");}}
class C extends B {void m1(C c) {System.out.print("C");}}
class D {
  public static void main(String[] args) {
    A a1 = new A(); B b1 = new B();
    C c1 = new C(); A c2 = new C();
    c2.m1(a1); c2.m1(b1); c2.m1(c1);
}}

What is the result of attempting to compile and run the program?

Question 24

class A {
  private static int f1 = 1;
  private int f2 = 2;
  void m1(int p1, final int p2) {
    int l1 = 5;
    final int l2 = 6;
    Object x = new Object() {
      int a = f1;  // 1
      int b = f2;  // 2
      int c = p1;  // 3
      int d = p2;  // 4
      int e = l1;  // 5
      int f = l2;  // 6
};}}

Compile-time errors are generated at which lines?

Question 25

class JMM106 {
  public static void main(String args[]) {
    int x = -5; int success = 0;
    do  {
      switch(x) {
        case 0: System.out.print("0"); x += 5; break;
        case 1: System.out.print("1"); x += 3; break;
        case 2: System.out.print("2"); x += 1; break;
        case 3: System.out.print("3"); success++; break;
        case 4: System.out.print("4"); x -= 1; break;
        case 5: System.out.print("5"); x -= 4; break;
        case 6: System.out.print("6"); x -= 5; break;
        default: x += x < 0 ? 2 : -2;
      }
    } while ((x != 3) || (success < 2));
}}

What is the result of attempting to compile and run the program?

Question 26

class Amber {
  public static void main(String[] args) {
    int[][] a = {{1,2},{0,1,2},{-1,0,2}};  // 1
    Object[] obj = (Object[])a.clone();    // 2
    for(int i = 0; i < obj.length; i++) {  // 3
      int[] ia = (int[])obj[i];            // 4
      System.out.print(ia[i]);             // 5
}}}

A compile-time error is generated at which line?

Question 27

class GFC307 {
  static void m1(int[] i1, int[] i2) {
    i1 = i2 = null;
  }
  public static void main (String[] args) {
    int[] i1 = {1}, i2 = {3}; m1(i1, i2);
    System.out.print(i1[0] + "," + i2[0]);
}}

What is the result of attempting to compile and run the program?

Question 28

class A11 {public String toString() {return "A11";}}
class A12 {
  public static void main(String[] arg) {
    A11[]     a1 = new A11[1];         // 1
    A11[][]   a2 = new A11[2][];       // 2
    A11[][][] a3 = new A11[3][][];     // 3
    a1[0] = new A11();                 // 4
    a2[0] = a2[1] = a1;                // 5
    a3[0] = a3[1] = a3[2] = a2;        // 6
    System.out.print(a3[2][1][0]);     // 7
}}

What is the result of attempting to compile and run the program?