Java Objective Questions and Answers

Given:
1. public class HorseTest {
2. public static void main(String[] args) {
3. class Horse {
4. public String name;
5. public Horse(String s) {
6. name = s;
7. }
8. }
9. Object obj = new Horse("Zippo");
10. System.out.println(obj.name);
11. }
12. }
What is the result?

The following block of code creates a Thread using a Runnable target:
Runnable target = new MyRunnable();
Thread myThread = new Thread(target);
Which of the following classes can be used to create the target, so that the preceding code
compiles correctly?

Given:
3. class MyThread extends Thread {
4. public static void main(String [] args) {
5. MyThread t = new MyThread();
6. Thread x = new Thread(t);
7. x.start();
8. }
9. public void run() {
10. for(int i=0;i<3;++i) {
11. System.out.print(i + "..");
12. } } }

What is the result of this code?

Given:
3. class Test {
4. public static void main(String [] args) {
5. printAll(args);
6. }
7. public static void printAll(String[] lines) {
8. for(int i=0;i<lines.length;i++){
9. System.out.println(lines[i]);
10. Thread.currentThread().sleep(1000);
11. } } }
The static method Thread.currentThread() returns a reference to the currently executing
Thread object. What is the result of this code?

Given:
public abstract class AbstractTest {
public int getNum() {
return 45;
}
public abstract class Bar {
public int getNum() {
return 38;
}
}
public static void main(String[] args) {
AbstractTest t = new AbstractTest() {
public int getNum() {
return 22;
}
};
AbstractTest.Bar f = t.new Bar() {
public int getNum() {
return 57;
}
};
System.out.println(f.getNum() + " " + t.getNum());
} }
What is the result?

Given:
3. public class Tour {
4. public static void main(String[] args) {
5. Cathedral c = new Cathedral();
6. // insert code here
7. s.go();
8. }
9. }
10. class Cathedral {
11. class Sanctum {
12. void go() { System.out.println("spooky"); }
13. }
14. }
Which, inserted independently at line 6, compile and produce the output "spooky"?

Given:
5. class A { void m() { System.out.println("outer"); } }
6.
7. public class TestInners {
8. public static void main(String[] args) {
9. new TestInners().go();
10. }
11. void go() {
12. new A().m();
13. class A { void m() { System.out.println("inner"); } }
14. }
15. class A { void m() { System.out.println("middle"); } }
16. }
What is the result?

Given:
3. public class City {
4. class Manhattan {
5. void doStuff() throws Exception { System.out.print("x "); }
6. }
7. class TimesSquare extends Manhattan {
8. void doStuff() throws Exception { }
9. }
10. public static void main(String[] args) throws Exception {
11. new City().go();
12. }
13. void go() throws Exception { new TimesSquare().doStuff(); }
14. }
What is the result?

Given:
3. public class Navel {
4. private int size = 7;
5. private static int length = 3;
6. public static void main(String[] args) {
7. new Navel().go();
8. }
9. void go() {
10. int size = 5;
11. System.out.println(new Gazer().adder());
12. }
13. class Gazer {
14. int adder() { return size * length; }
15. }
16. }
What is the result?

Given:
3. import java.util.*;
4. public class Pockets {
5. public static void main(String[] args) {
6. String[] sa = {"nickel", "button", "key", "lint"};
7. Sorter s = new Sorter();
8. for(String s2: sa) System.out.print(s2 + " ");
9. Arrays.sort(sa,s);
10. System.out.println();
11. for(String s2: sa) System.out.print(s2 + " ");
12. }
13. class Sorter implements Comparator<String> {
14. public int compare(String a, String b) {
15. return b.compareTo(a);
16. }
17. }
18. }
What is the result?

Given:
class CardBoard {
Short story = 200;
CardBoard go(CardBoard cb) {
cb = null;
return cb;
}
public static void main(String[] args) {
CardBoard c1 = new CardBoard();
CardBoard c2 = new CardBoard();
CardBoard c3 = c1.go(c2);
c1 = null;
// do Stuff
} }
When // doStuff is reached, how many objects are eligible for GC?

Given:
class Alien {
String invade(short ships) { return "a few"; }
String invade(short... ships) { return "many"; }
}
class Defender {
public static void main(String [] args) {
System.out.println(new Alien().invade(7));
} }

What is the result?

Given:
1. class Dims {
2. public static void main(String[] args) {
3. int[][] a = {{1,2,}, {3,4}};
4. int[] b = (int[]) a[1];
5. Object o1 = a;
6. int[][] a2 = (int[][]) o1;
7. int[] b2 = (int[]) o1;
8. System.out.println(b[1]);
9. } }
What is the result?

Given:
class Mixer {
Mixer() { }
Mixer(Mixer m) { m1 = m; }
Mixer m1;
public static void main(String[] args) {
Mixer m2 = new Mixer();
Mixer m3 = new Mixer(m2); m3.go();
Mixer m4 = m3.m1; m4.go();
Mixer m5 = m2.m1; m5.go();
}
void go() { System.out.print("hi "); }
}
What is the result?

Given:
class Fizz {
int x = 5;
public static void main(String[] args) {
final Fizz f1 = new Fizz();
Fizz f2 = new Fizz();
Fizz f3 = FizzSwitch(f1,f2);
System.out.println((f1 == f3) + " " + (f1.x == f3.x));
}
static Fizz FizzSwitch(Fizz x, Fizz y) {
final Fizz z = x;
z.x = 6;
return z;
} }
What is the result?