Monday, September 16, 2013

Core Java practice questions-2

Below are the second set of core java practice questions helpful for OCJP/SCJP preparation.


11) For loop and operators(AND OR) preincrement

public class Test {

public static void main(String[] args) {
int a=0;
int b=0;

for(short index=0; index<5;index++){
if ((++a>2)|(++b>2)){
a++;
}
}
System.out.println(a+" "+b);
}
}

Ans:-8 5
--------------------------------------------------------------------
12) For loop and operators(AND,OR) preincrement

public class Test {

public static void main(String[] args) {
int a=0;
int b=0;

for(short index=0; index<5;index++){
if ((++a>2)&&(++b>2)){
a++;
}
}
System.out.println(a+" "+b);
}
}

Ans:-6 3
-------------------------------------------------------------------------
13)For loop and operators(AND,OR) postincrement

public class Test {

public static void main(String[] args) {
int a=0;
int b=0;

for(short index=0; index<5;index++){
if ((a++>2)||(b++>2)){
a++;
}
}
System.out.println(a+" "+b);
}
}

Ans:- 7 3
-------------------------------------------------------------------------
14)For loop and operators(AND,OR) postincrement

public class Test {

public static void main(String[] args) {
int a=0;
int b=0;

for(short index=0; index<5;index++){
if ((a++>2)||(b++>2)){
a++;
}
}
System.out.println(a+" "+b);
}
}

Ans 7 5
---------------------------------------------------------------------------
15)For loop and operators(AND,OR) postincrement

public class Test {

public static void main(String[] args) {
int a=0;
int b=0;

for(short index=0; index<5;index++){
if ((a++>2)&&(b++>2)){
a++;
}
}
System.out.println(a+" "+b);
}
}

Ans :- 5 2
----------------------------------------------------------------------------------
16)For loop and operators(AND,OR) postincrement

public class Test {

public static void main(String[] args) {
int a = 10, b = 5;
for (int i = 0; i < 5; i++, b--) {
if (a > 2) {
a--;
}
if (a > 5) {
--a;
continue;
}
}
System.out.println(a + " " + b);
}

}
Ans:- 3 0
-----------------------------------------------------------------------------------
17)switch and local variables should be initialises
public static void main(String[] args) {
String strln1;
int i = (int)(4*3);
switch(i){
case 0:
strln1 = "case 0";
break;
case 1:
strln1 = "case 1";
break;
case 2:
strln1 = "case 2";
break;
default:
System.out.println("in default");
}
System.out.println(strln1);

Ans :- in default null
------------------------------------------------------------------------------------
18)switch and local variables should be initialises
public class Test {
public static void main(String[] args){
final int x=2;
for (int i = 0; i < 3; i++) {
switch(i)
{
case x:System.out.println("Hello");
case x-1:System.out.println("second");
break;
default:System.out.println("default");
case x-2:System.out.println("fourth");
}
}
}
}

Ans:- fourth
second
Hello
second
-----------------------------------------------------------------
19) switch and local variables should be initialises
public class Test {
public static void main(String[] args){
int x=2;
for (int i = 0; i < 3; i++) {
switch(i)
{
case x:System.out.println("Hello");
case x-1:System.out.println("second");
break;
default:System.out.println("default");
case x-2:System.out.println("fourth");
}
}
}
}

Ans:- compile time error ,case statement needs a constant expression

----------------------------------------------------------------------------
20) Local variable and Instance variable

public class Test {

int count;

public void method1(){
System.out.println("method 1");
}

public static void main (String [] args){
int count=12;
Test obj= new Test();
System.out.println(obj.count);
System.out.println(count);
}
}

Ans:- 0
12



Happy Learning

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