Dan Chisholm's
Java Programmer Certification Mock Exam

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Question 1

class B {
  private String name;
  public B(String s) {name = s;}
  protected void finalize() {System.out.print(name);}
}
class E {
  public static void m() {
    B x1 = new B("X"), y1 = new B("Y");
  }
  public static void main(String[] args) {
    m(); System.gc();
}}

Which of the following could not be a result of attempting to compile and run the program?

Question 2

void m1() {
  Q q1 = null;
  for (int i = 0; i < 10; i++) {
    q1 = new Q();   // 1
    m2(q1);         // 2
  }
  System.out.print("All done"); // 3
}

When the processing of line 3 begins, how many objects of type Q that were created at line 1 have become eligible for garbage collection?

Question 3

class Q {
  private int id;
  protected void finalize() {System.out.print(id);}
  public Q(int i) {id = i;}
}
class R {
  public static void main(String[] args) {
    Q q1 = null;
    for (int i = 0; i < 10; i++) {q1 = new Q(i);} // 1
    System.gc();     // 2
}}

When the processing of line 2 begins, how many objects of type Q that were created at line 1 have become eligible for garbage collection?

Question 4

class I {
  private I other;
  public void other(I i) {other = i;}
}
class J {
  private void m1() {
    I i1 = new I(), i2 = new I();
    I i3 = new I(), i4 = new I();
    i1.other(i3); i2.other(i1);
    i3.other(i2); i4.other(i4);
  }
  public static void main (String[] args) {
    new J().m1();
}}

Which object is not eligible for garbage collection after method m1 returns?

Question 5

class I {
  private String name;
  public I(String s) {name = s;}
  private I other;
  public void other(I i) {other = i;}
}
class J {
  private I i1 = new I("A"), i2 = new I("B"), i3 = new I("C");
  private void m1() {
    i1.other(i2); i2.other(i1); i3.other(i3);
    i1 = i3; i2 = i3;
    m2();
  }
  private void m2() {/* Do amazing things. */}
  public static void main (String[] args) {
    new J().m1();
}}

Which of the three objects, A, B or C, is not eligible for garbage collection when method m2 begins to execute?

Question 6

class I {
  private String name;
  protected void finalize() {System.out.print(name);}
  public I(String s) {name = s;}
}
class J {
  private static void m1(I[] a1) {
    a1[0] = a1[1] = a1[2] = null;
  }
  public static void main (String[] args) {
    I[] a1 = new I[3];   // 1
    a1[0] = new I("A");  // 2
    a1[1] = new I("B");  // 3
    a1[2] = new I("C");  // 4
    m1(a1);
    System.gc();
}}

After method m1 returns, the object created on which line is not eligible for garbage collection?

Question 7

class I {
  private String name;
  public String toString() {return name;}
  public I(String s) {name = s;}
}
class J {
  private static void m1(I[] a1) {a1 = null;}
  public static void main (String[] args) {
    I[] a1 = new I[3];   // 1
    a1[0] = new I("A");  // 2
    a1[1] = new I("B");  // 3
    a1[2] = new I("C");  // 4
    m1(a1);
    for (int i = 0; i < a1.length; i++) {
      System.out.print(a1[i]);
}}}

After method m1 returns, the object created on which line is eligible for garbage collection?

Question 8

class A {
  private String name;
  private A otherA;
  public A(String name) {this.name = name;}
  public void other(A otherA) {this.otherA = otherA;}
  public A other() {return otherA;}
  public String toString() {return name;}
  protected void finalize() {System.out.print(name);}
}
class B {
  public static void m1() {
    A a1 = new A("A1"), a2 = new A("A2"), a3 = new A("A3"), a0 = a3;
    a1.other(a2); a2.other(a3); a3.other(a1);
    for(int i = 0; i<4; i++){System.out.print(a0 = a0.other());}
  }
  public static void main(String[] args) {m1(); System.gc();}
}

Which of the following could be a result of attempting to compile and run the program?

Question 9

class B {
  private String name;
  public B(String name) {this.name = name;}
  public String toString() {return name;}
  protected void finalize() {System.out.print(name);}
}
class H {
  static B ba = new B("Ba");
  static int i = 1;
  static B m1(B b) {return b = new B("B" + i++);}
  public static void main (String[] args) {
    B x = m1(ba); m1(x); 
    System.out.println(", " + ba + ", " + x);
}}

Which of the following could be a result of attempting to compile and run the program?

Question 10

class B {
  private String name;
  public B(String name) {this.name = name;}
  public String toString() {return name;}
  protected void finalize() {System.out.print(name);}
}
class J {
  static B bc;
  static int i = 1;
  static B m1(B b) {bc = b; return new B("B" + i++);}
  public static void main (String[] args) {
    B x = m1(new B("Ba")), y = m1(new B("Bb"));
    System.out.println(", " + x + ", " + y + ", " + bc);
}}

Which of the following could be a result of attempting to compile and run the program?

Question 11

class I {
  private String name;
  public String name() {return name;}
  public I(String s) {name = s;}
}
class J {
  public static void m1(I i) {i = null;}
  public static void main (String[] args) {
    I i = new I("X");           // 1
    m1(i);                      // 2
    System.out.print(i.name()); // 3
}}

Which of the following is a true statement?