Dan Chisholm's
Java Programmer Certification Mock Exam

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Question 1

class Basics {
  int x = 1, y = 2;
  public static void main (String[] args) {System.out.println(x+y);}
}

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

Question 2

Which of these words belongs to the set of Java keywords?

Question 3

class MCZ18 {
  public static void main (String[] args) {
    String a = "abcd";          // 1
    String b = "'\u0041'";      // 2
    String c = "\u0041";        // 3
    String d = "\uD7AF";        // 4
    System.out.print(a+b+c+d);  // 5
}}

A compile-time error is generated at which line?

Question 4

class GFC506 {private String name;}
class GFC507 extends GFC506 {
  String name;
  public void setName(String name) {this.name = name;}
  public String getName() {return name;}
}
class GFC508 extends GFC506 {
  private String name;
  public GFC508(String name) {setName(name);}
  public void setName(String name) {this.name = name;}
  public String getName() {return name;}
}

Which class is not tightly encapsulated?

Question 5

class SRC112 {
  static String m(byte i) {return "byte";}
  static String m(int i) {return "int";}
  static String m(long i) {return "long";}
  static String m(double i) {return "double";}
  public static void main (String[] args) {
    byte b = 0;
    System.out.print(m(Math.min(b,b))+",");
    System.out.print(m(Math.min(b,1))+",");
    System.out.print(m(Math.min(b,1L)));
}}

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

Question 6

class F {
  public static void main (String[] args) {
    Integer i1 = new Integer("1");
    Integer i2 = new Integer("1");
    int h1 = i1.hashCode(), h2 = i2.hashCode();
    StringBuffer sb1 = new StringBuffer("1");
    StringBuffer sb2 = new StringBuffer("1");
    int h3 = sb1.hashCode(), h4 = sb2.hashCode();
    System.out.print((h1==h2)+","+(h3==h4));
}}

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

Question 7

class F {
  public static void main (String args[]) {
    Double d1 = new Double("0x10");         // 1
    double d2 = Double.parseDouble("0x10"); // 2
    Double d3 = Double.valueOf("0x10");     // 3
    System.out.print(d1+","+d2+","+d3);
}}

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

Question 8

Which of the following classes allow unsynchronized read operations by multiple threads?

Question 9

class MWC209 {
  public static void main(String[] args) {
    int[][] a1 = [[1,2],[3,4,5],[6,7,8,9]];
    int[][] a2 = [[1,2],[3,4,5],[6,7,8,9]];
    int[][] a3 = [[1,2],[3,4,5],[6,7,8,9]];
    System.out.print(a1[0][1]+","+a2[1][2]+","+a3[2][3]);
}}

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

Question 10

class A {
  int B;        // 1
  void B() {}   // 2
  class B {}    // 3
}

Which line results in a compile-time error?

Question 11

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

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

Question 12

interface A {
  int a = 1;                        // 1
  public int b = 2;                 // 2
  public static int c = 3;          // 3
  public static final int d = 4;    // 4
}

Which field declaration results in a compile-time error?

Question 13

class Color {}
class Red extends Color {}
class Blue extends Color {}
class A {
  public static void main (String[] args) {
    Color color1 = new Red(); Red color2 = new Red();
    boolean b1 = color1 instanceof Color;
    boolean b2 = color1 instanceof Blue;
    boolean b3 = color2 instanceof Blue;
    System.out.print(b1+","+b2+","+b3);
}}

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

Question 14

class A {void m1(String s1) {}}
class B extends A {
  void m1(String s1) {}  // 1
  void m1(boolean b) {}  // 2
  void m1(byte b) throws Exception {}  // 3
  String m1(short s) {return new String();} //4
  private void m1(char c) {} // 5
  protected void m1(int i) {} // 6
}

What is the result of attempting to compile the program?

Question 15

class MWC110 {
  static void m1(String s1, String s2) {
    s1.insert(1,"D"); s1 = s1 + s2;
  }
  public static void main(String[] s) {
    String s1 = "A", s2 = "B";
    m1(s1,s2);
    System.out.print(s1 + s2);
}}

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

Question 16

class SRC113 {
  static String m(byte i) {return "byte";}
  static String m(short i) {return "short";}
  static String m(char i) {return "char";}
  static String m(int i) {return "int";}
  static String m(long i) {return "long";}
  static String m(float i) {return "float";}
  static String m(double i) {return "double";}
  public static void main (String[] args) {
    byte b = 0; short s = 0; char c = 0;
    System.out.print(m(Math.min(b,1L))+",");
    System.out.print(m(Math.min(s,1.0f))+",");
    System.out.print(m(Math.min(c,1.0)));
}}

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

Question 17

class A {String s1 = "A";}
class B extends A {String s1 = "B";}
class C extends B {String s1 = "C";}
class D {
  static void m1(A x) {System.out.print(x.s1);}
  static void m1(B x) {System.out.print(x.s1);}
  static void m1(C x) {System.out.print(x.s1);}
  public static void main(String[] args) {
    A a; B b; C c; a = b = c = new C(); m1(a); m1(b); m1(c);
}}

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

Question 18

class Red {
  static class StaticNested {interface ABC {}}  // 1
  class NonStaticInner {interface DEF {}}       // 2
  interface GHI {}                              // 3
}

A compile-time error is generated at which line?

Question 19

Which of the following is a true statement?

Question 20

class MWC109 {
  public static void main(String args[]) {
    String a = "A", b = "B", c = a+b, d = a+b;
    System.out.print(((a+b)==(a+b)) + ",");
    System.out.print((c==d) + ",");
    System.out.print(c.equals(d));
}}

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

Question 21

import java.util.*;
class GFC109 {
  public static void main (String[] args) {
    Object v = new Vector();
    System.out.print((v instanceof Collections)+",");
    System.out.print((v instanceof Arrays)+",");
    System.out.print(v instanceof List);
}}

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

Question 22

class GFC214 {
  static void m1(boolean b1) {System.out.print("boolean ");}
  static void m1(byte b1) {System.out.print("byte ");}
  static void m1(short s1) {System.out.print("short ");}
  static void m1(char c1) {System.out.print("char ");}
  static void m1(int i1) {System.out.print("int ");}
  public static void main(String[] args) {
    byte b1; m1(b1 = 1); m1(b1); m1(b1 == 1);
}}

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

Question 23

class A {
  private static int counter;
  public static int getCounter(){return counter++;}
  private static int innerCounter;
  public static int getInnerCounter(){return innerCounter++;}
  private String name;
  A() {name = "A" + getCounter();}
  class B {
    private String name;
    B() {
      name = "B" + getInnerCounter();
      System.out.print(A.this.name + name); // 1
  }}
  public static void main(String[] args) {
    new A().new B();  // 2
    A a1 = new A();
    a1.new B();       // 3
    a1.new B();       // 4
}}

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

Question 24

Which of the following thread state transitions model the lifecycle of a thread?

Question 25

class A {}  class B extends A {}
class C extends B {
  static void m1(A x) {System.out.print("m1A");}
  static void m2(B x) {System.out.print("m2B"); m1(x);}
  static void m2(A x) {System.out.print("m2A"); m1(x);}
  static void m3(C x) {System.out.print("m3C"); m2(x);}
  static void m3(B x) {System.out.print("m3B"); m2(x);}
  static void m3(A x) {System.out.print("m3A"); m2(x);}
  public static void main(String[] args) {m3(new C());}
}

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

Question 26

class JMM110 {
  public static void main (String[] args) {
    int j = 0;
    do for (int i = 0; i++ < 2;)
      System.out.print(i);
    while (j++ < 2);
}}

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

Question 27

An assert statement can be used to check a control-flow invariant to verify which of the following?

Question 28

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?