Question1: Which statement will empty the contents of a StringBuilder variable named sb?
A. sb.delete(0, sb.length());
B. sb.delete(0, sb.size());
C. sb.deleteAll();
D. sb.removeAll()
Answer: A
Questions2: Given below program: What is the result of below program:
class Vehicle {
int x;
Vehicle(){
this(10); // Line N1
}
Vehicle(int x){
this.x = x;
}
}
public class Car extends Vehicle {
int y;
Car(){
super();
this(20); // Line N2
}
Car(int y){
this.y=y;
}
@Override
public String toString() {
return super.x + ":"+this.y;
}
public static void main(String[] args) {
Vehicle y = new Car();
System.out.println(y);
}
}
A. 10:20
B. 0:20
C. Compilation fails at line n1
D. Compilation fails at line n2
Answer: D :
Explanation: At line N2, It will throw error “Constructor call must be the first statement in a constructor”. Super(),this() can not be placed , only either super, this allowed
this(...) part) or to a constructor in the super class (using super(...)) must go in the first line. It’s a way to ensure that the parent’s state is initialized before initializing the current object.Question3: What is the result of below program?
public class CallerTest {
public static void main(String[] args) {
Caller c = new Caller();
c.start();
c.init();
}
}
class Caller {
private void init() {
System.out.println("Initialized");
}
private void start() {
init();
System.out.println("Started");
}
}
A. An exception is thrown at runtime.
B. InitializedStartedInitialized
C. InitializedStarted
D. Compilation fails.
Answer: D Start, init methods visibility must be either default,protected and public
Question4: Given the below program, what is the result
public class TestCode {
public static void main(String[] args) {
TestCode test = new TestCode();
System.out.println(isExists+"");
isExists = test.doSomething();
System.out.println(isExists);
}
public static boolean doSomething() {
return !isExists;
}
static boolean isExists = false;
}
A. Compilation fails.
B. false true
C. true false
D. true true
E. false false
Answer: B. As shown in below, The program executes and static methods can be accessed from object too
Question5:
public class TerneryOperation {
public static void main(String[] args) {
String stuff = "TV";
String res = null;
if(stuff.equals("TV")) {
res = "Walter";
}else if(stuff.equals("Movie")) {
res = "White";
}else {
res = "No Result";
}
}
}
Which code fragment can replace the if block?
A. stuff.equals(“TV”)? res=”Walter”:stuff.equals(“Movie”)? res=”white”:res=”No Result”;
B. res = stuff.equals(“TV”)? “Walter” else stuff.equals(“Movie”)? “white”: “No Result”;
C. res = stuff.equals(“TV”)? stuff.equals(“Movie”)? “Walter”: “white”: “No Result”;
D. res = stuff.equals(“TV”)? “Walter”:stuff.equals(“Movie”)? “white”: “No Result”;
Answer: D
Question6: What is the result of below program?
public class TestOperator {
public static void main(String[] args) {
int x=1;
int y=0;
if(x++ > ++y) {
System.out.println("Hello");
}else {
System.out.println("Welcome");
}
System.out.println("Log "+x+":"+y);
}
}
A. Hello Log 1:0
B. Hello Log 2:1
C. Welcome Log 2:1
D. Welcome Log 1:0
Answer: C
Question7: What is the result of below program?
public class TestOperator {
public static void main(String[] args) {
int x=1;
int y=0;
if(x++ > y++) {
System.out.println("Hello");
}else {
System.out.println("Welcome");
}
System.out.println("Log "+x+":"+y);
}
}
A. Hello Log 1:0
B. Hello Log 2:1
C. Welcome Log 2:1
D. Welcome Log 1:0
