document7

Questions no -1 What is the output for the below code ?

class A implements Runnable{public void run(){

System.out.println(Thread.currentThread().getName());}

}

public class Test {public static void main(String... args) {

A a = new A();Thread t = new Thread(a);Thread t1 = new Thread(a);t.setName("t");t1.setName("t1");t.setPriority(10);t1.setPriority(-3);t.start();t1.start();

}}

Options are

A.t t1B.t1 tC.t tD.Compilation succeed but Runtime Exception

Answer :D is the correct answer.

Thread priorities are set using a positive integer, usually between 1 and 10. t1.setPriority(-3); throws java.lang.IllegalArgumentException.


class A implements Runnable{public void run(){

System.out.println(Thread.currentThread().getName());}

}

1. public class Test {2. public static void main(String... args) {

3. A a = new A();4. Thread t = new Thread(a);5. t.setName("good");6. t.start();7. }8. }

Options are

A.goodB.nullC.Compilation fails with an error at line 5D.Compilation succeed but Runtime Exception

Answer :A is the correct answer.

Thread.currentThread().getName() return name of the current thread.


public class Test {

public static void main(String[] args) {Boolean expr = true;if (expr) {

System.out.println("true");} else {

System.out.println("false");}

}

}

optionsA)trueB)Compile Error - can't use Boolean object in if().C)falseD)Compile Properly but Runtime Exception.

Correct answer is : A

Explanations : In the if statement, condition can be Boolean object in jdk1.5 and jdk1.6.In the previous version only boolean is allowed.Questions no -4 What is the output for the below code ?

public class Test {

public static void main(String[] args) {List<Integer> list = new ArrayList<Integer>(); list.add(0, 59);int total = list.get(0);System.out.println(total);

}

}

optionsA)59B)Compile time error, because you have to do int total = ((Integer)(list.get(0))).intValue();C)Compile time error, because can't add primitive type in List.D)Compile Properly but Runtime Exception.


Explanations :Manual conversion between primitive types (such as an int) and wrapper classes

(such as Integer) is necessary when adding a primitive data type to a collection in jdk1.4 but

The new autoboxing/unboxing feature eliminates this manual conversion in jdk 1.5 and jdk 1.6.


public class Test {

public static void main(String[] args) {Integer i = null;int j = i;System.out.println(j);

}

}

optionsA)0B)Compile with error C)nullD)NullPointerException

Correct answer is : D

Explanations :An Integer expression can have a null value. If your program tries to autounbox null, it will throw a NullPointerException.Questions no -4 What is the output for the below code ?

public class Outer {private int a = 7; class Inner { public void displayValue() { System.out.println("Value of a is " + a); } }}

public class Test {

public static void main(String... args) throws Exception {Outer mo = new Outer(); Outer.Inner inner = mo.new Inner(); inner.displayValue();

}

}

optionsA)Value of a is 7B)Compile Error - not able to access private member.C)Runtime ExceptionD)Value of a is 8


Explanations : An inner class instance can never stand alone without a direct relationship to an instance of the outer class.

you can access the inner class is through a live instance of the outer class.

Inner class can access private member of the outer class.


public class B {

public String getCountryName(){return "USA";

}

public StringBuffer getCountryName(){StringBuffer sb = new StringBuffer();sb.append("UK");return sb;

}

public static void main(String[] args){B b = new B();System.out.println(b.getCountryName().toString());

}

}

optionsA)Compile with errorB)USAC)UKD) Runtime Exception


Explanations : You cannot have two methods in the same class with signatures that only differ by return type.Questions no -6What is the output for the below code ?

public class C {

}

public class D extends C{

}

public class A {

public C getOBJ(){System.out.println("class A - return C");return new C();

}

}

public class B extends A{

public D getOBJ(){System.out.println("class B - return D");return new D();

}

}

public class Test {

public static void main(String... args) { A a = new B(); a.getOBJ();

}}

optionsA)Compile with error - Not allowed to override the return type of a method with a subtype of the original type.B)class A - return CC)class B - return DD) Runtime Exception

Correct answer is : C

Explanations : From J2SE 5.0 onwards. You are now allowed to override the return type of a method with a subtype of the original type.Questions no -7What is the output for the below code ?

public class A {

public String getName() throws ArrayIndexOutOfBoundsException{return "Name-A";

}

}

public class C extends A{

public String getName() throws Exception{return "Name-C";

}

}


A a = new C();a.getName();

}

}

optionsA)Compile with errorB)Name-AC)Name-CD)Runtime Exception


Explanations : Exception Exception is not compatible with throws clause in A.getName().

Overridden method should throw only same or sub class of the exception thrown by super class method.Questions no -8 What is the output for the below code ?

import java.util.regex.Matcher;import java.util.regex.Pattern;

public class Test {

public static void main(String... args) {

Pattern p = Pattern.compile("a*b");Matcher m = p.matcher("b");boolean b = m.matches();System.out.println(b);

}}

optionsA)trueB)Compile ErrorC)false

D)b


Explanations : a*b means "a" may present zero or more time and "b" should be present once.Questions no -9 What is the output for the below code ?

public class Test {


String input = "1 fish 2 fish red fish blue fish";Scanner s = new Scanner(input).useDelimiter("\\s*fish\\s*");System.out.println(s.nextInt());System.out.println(s.nextInt());System.out.println(s.next());System.out.println(s.next());s.close();

}}

optionsA)1 2 red blueB)Compile Error - because Scanner is not defind in java.C)1 fish 2 fish red fish blue fishD)1 fish 2 fish red blue fish


Explanations : java.util.Scanner is a simple text scanner which can parse primitive types and strings using regular expressions.Questions no -10 What is the output for the below code ?

public class Test {


Pattern p = Pattern.compile("a{3}b?c*");Matcher m = p.matcher("aaab");boolean b = m.matches();System.out.println(b);

}}

optionsA)trueB)Compile Error C)falseD)NullPointerException


Explanations :X? X, once or not at all X* X, zero or more times X+ X, one or more times X{n} X, exactly n times X{n,} X, at least n times X{n,m} X, at least n but not more than m timesQuestions no -11 What is the output for the below code ?

public class Test {


Pattern p = Pattern.compile("a{1,3}b?c*");Matcher m = p.matcher("aaab");boolean b = m.matches();System.out.println(b);

}}

optionsA)trueB)Compile Error C)falseD)NullPointerException


Explanations :X? X, once or not at all X* X, zero or more times X+ X, one or more times X{n} X, exactly n times X{n,} X, at least n times X{n,m} X, at least n but not more than m timesQuestions no -12 What is the output for the below code ?

public class A {public A() {

System.out.println("A"); }}

public class B extends A implements Serializable {public B() {

System.out.println("B"); }

}

public class Test {

public static void main(String... args) throws Exception {B b = new B();

ObjectOutputStream save = new ObjectOutputStream(new FileOutputStream("datafile")); save.writeObject(b); save.flush();

ObjectInputStream restore = new ObjectInputStream(new FileInputStream("datafile")); B z = (B) restore.readObject();

}

}

optionsA)A B AB)A B A BC)B BD)A B


Explanations :On the time of deserialization , the Serializable object not create new object. So constructor of class B does not called. A is not Serializable object so constructor is called.Questions no -13 What is the output for the below code ?

public class A {}

public class B implements Serializable {A a = new A();public static void main(String... args){

B b = new B();try{

FileOutputStream fs = new FileOutputStream("b.ser");ObjectOutputStream os = new ObjectOutputStream(fs);os.writeObject(b);os.close();

}catch(Exception e){e.printStackTrace();

}

}

}

optionsA)Compilation FailB)java.io.NotSerializableException: Because class A is not Serializable.C)Run properlyD)Compilation Fail : Because class A is not Serializable.

Correct answer is : B

Explanations :It throws java.io.NotSerializableException:A Because class A is not Serializable.

When JVM tries to serialize object B it will try to serialize A also because (A a = new A()) is instance variable of Class B.

So thows NotSerializableException.

Questions no -14 What is the output for the below code running in the same JVM?

public class A implements Serializable {transient int a = 7; static int b = 9;

}

public class B implements Serializable {

public static void main(String... args){A a = new A();try { ObjectOutputStream os = new ObjectOutputStream( new FileOutputStream("test.ser")); os.writeObject(a); os. close();

System.out.print( + + a.b + " ");

ObjectInputStream is = new ObjectInputStream(new FileInputStream("test.ser"));

A s2 = (A)is.readObject(); is.close(); System.out.println(s2.a + " " + s2.b); } catch (Exception x) { x.printStackTrace(); }

}

}

optionsA)9 0 9B)9 7 9C)0 0 0D)0 7 0


Explanations :transient variables are not serialized when an object is serialized.

In the case of static variable you can get the values in the same JVM.


public enum Test {BREAKFAST(7, 30), LUNCH(12, 15), DINNER(19, 45);

private int hh;

private int mm;

Test(int hh, int mm) {assert (hh >= 0 && hh <= 23) : "Illegal hour.";assert (mm >= 0 && mm <= 59) : "Illegal mins.";this.hh = hh;this.mm = mm;

}

public int getHour() {return hh;

}

public int getMins() {return mm;

}

public static void main(String args[]){Test t = new BREAKFAST;System.out.println(t.getHour() +":"+t.getMins());

}}

optionsA)7:30B)Compile Error - an enum cannot be instantiated using the new operator.C)12:50D)19:45


Explanations : As an enum cannot be instantiated using the new operator, the constructors cannot be called explicitly.You have to do like Test t = BREAKFAST;Questions no -16 What is the output for the below code ?

public class Test {enum Day {

MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY}enum Month {

JAN, FEB}

public static void main(String[] args) {

int[] freqArray = { 12, 34, 56, 23, 5, 13, 78 };

// Create a Map of frequenciesMap<Day, Integer> ordinaryMap = new HashMap<Day, Integer>();for (Day day : Day.values()) {

ordinaryMap.put(day, freqArray[day.ordinal()]);}

// Create an EnumMap of frequenciesEnumMap<Day, Integer> frequencyEnumMap = new EnumMap<Day,

Integer>(ordinaryMap);

// Change some frequenciesfrequencyEnumMap.put(null, 100);

System.out.println("Frequency EnumMap: " + frequencyEnumMap);

}

}

optionsA)Frequency EnumMap: {MONDAY=12, TUESDAY=34, WEDNESDAY=56, THURSDAY=23, FRIDAY=5, SATURDAY=13, SUNDAY=78}B)Compile Error C)NullPointerExceptionD)Frequency EnumMap: {MONDAY=100, TUESDAY=34, WEDNESDAY=56, THURSDAY=23, FRIDAY=5, SATURDAY=13, SUNDAY=123}


Explanations : The null reference as a key is NOT permitted.Questions no -17 public class EnumTypeDeclarations {

public void foo() {

enum SimpleMeal { BREAKFAST, LUNCH, DINNER

}}

}

Is the above code Compile without error ?

optionsA)Compile without errorB)Compile with errorC)Compile without error but Runtime ExceptionD)Compile without error but Enum Exception


Explanations :An enum declaration is a special kind of class declaration:

a) It can be declared at the top-level and as static enum declaration.

b) It is implicitly static, i.e. no outer object is associated with an enum constant.

c) It is implicitly final unless it contains constant-specific class bodies, but it can implement interfaces.

d) It cannot be declared abstract unless each abstract method is overridden in the constant-specific class body of every enum constant.

e) Local (inner) enum declaration is NOT OK!

Here inpublic void foo() {

enum SimpleMeal { BREAKFAST, LUNCH, DINNER

}}

enum declaration is local within method so compile time error.Questions no -18 What is the output for the below code ?

public enum Test {int t;BREAKFAST(7, 30), LUNCH(12, 15), DINNER(19, 45);

private int hh;

private int mm;

Test(int hh, int mm) {assert (hh >= 0 && hh <= 23) : "Illegal hour.";assert (mm >= 0 && mm <= 59) : "Illegal mins.";this.hh = hh;this.mm = mm;

}

public int getHour() {return hh;

}

public int getMins() {return mm;

}

public static void main(String args[]){Test t = BREAKFAST;System.out.println(t.getHour() +":"+t.getMins());

}}

optionsA)7:30B)Compile Error C)12:15D)19:45


Explanations : The enum constants must be declared before any other declarations in an enum type.

In this case compile error because of declaration int t; before enum declaration.

Questions no -19

What is the output for the below code ?

public class B extends Thread{public static void main(String argv[]){B b = new B();b.run();} public void start(){for (int i = 0; i < 10; i++){System.out.println("Value of i = " + i); } }}

optionsA)A compile time error indicating that no run method is defined for the Thread classB)A run time error indicating that no run method is defined for the Thread classC)Clean compile and at run time the values 0 to 9 are printed outD)Clean compile but no output at runtime


Explanations : This is a bit of a sneaky one as I have swapped around the names of the methods you need to define and call when running a thread. If the for loop were defined in a method called public void run() and the call in the main method had been to b.start() The list of values from 0 to 9 would have been output.Questions no -20


public class Test extends Thread{

static String sName = "good"; public static void main(String argv[]){ Test t = new Test(); t.nameTest(sName); System.out.println(sName); } public void nameTest(String sName){ sName = sName + " idea "; start(); } public void run(){ for(int i=0;i < 4; i++){ sName = sName + " " + i; } }

}

optionsA)goodB)good ideaC)good idea good ideaD)good 0 good 0 1


Explanations : Change value in local methods wouldn’t change in global in case of String ( because String object is immutable).Questions no -21 What is the output for the below code ?

public class Test{public static void main(String argv[]){Test1 pm1 = new Test1("One");pm1.run();Test1 pm2 = new Test1("Two");pm2.run();

}}

class Test1 extends Thread{private String sTname="";Test1(String s){

sTname = s;

}public void run(){

for(int i =0; i < 2 ; i++){try{ sleep(1000);}catch(InterruptedException e){}

yield();System.out.println(sTname);}

}}

optionsA)Compile errorB)One One Two TwoC)One Two One TwoD)One Two


Explanations : If you call the run method directly it just acts as any other method and does not return to the calling code until it has finished. executingQuestions no -22 What is the output for the below code ?

public class Test extends Thread{ public static void main(String argv[]){ Test b = new Test(); b.start(); } public void run(){ System.out.println("Running"); }}

optionsA)Compilation clean and run but no outputB)Compilation and run with the output "Running"C)Compile time error with complaint of no Thread importD)Compile time error with complaint of no access to Thread package


Explanations :The Thread class is part of the core java.lang package and does not need any explicit import statement.Questions no -23 What is the output for the below code ?

public class Tech { public void tech() { System.out.println("Tech"); }

}

public class Atech {

Tech a = new Tech() { public void tech() { System.out.println("anonymous tech"); } }; public void dothis() {

a.tech(); }

public static void main(String... args){Atech atech = new Atech();atech.dothis();

}

optionsA)anonymous techB)Compile Error C)TechD)anonymous tech Tech


Explanations : This is anonymous subclass of the specified class type.

Anonymous inner class ( anonymous subclass ) overriden the Tech super class of tech() method.

Therefore Subclass method will get called.Questions no -24 What is the output for the below code ?

public class Outer { private String x = "Outer variable"; void doStuff() { String z = "local variable"; class Inner { public void seeOuter() { System.out.println("Outer x is " + x); System.out.println("Local variable z is " + z); } } }

}

optionsA)Outer x is Outer variable.B)Compile Error C)Local variable z is local variable.D)Outer x is Outer variable Local variable z is local variable


Explanations : Cannot refer to a non-final variable z inside an inner class defined in a different method.Questions no -25


public class Test {

public static void main(String... args) {for(int i = 2; i < 4; i++)

for(int j = 2; j < 4; j++) assert i!=j : i;

}}

optionsA)The class compiles and runs, but does not print anything.B)The number 2 gets printed with AssertionErrorC)The number 3 gets printed with AssertionErrorD)compile error


Explanations : When i and j are both 2, assert condition is false, and AssertionError gets generated. Questions no -26


public class Test {

public static void main(String... args) {for(int i = 2; i < 4; i++)

for(int j = 2; j < 4; j++)if(i < j)

assert i!=j : i;

}}

optionsA)The class compiles and runs, but does not print anything.B)The number 2 gets printed with AssertionErrorC)The number 3 gets printed with AssertionErrorD)compile error


Explanations : When if condition returns true, the assert statement also returns true.Hence AssertionError not generated.Questions no -26 What is the output for the below code ?

public class NameBean {private String str;

NameBean(String str ){this.str = str;

}

public String toString() {return str;

}}

import java.util.HashSet;

public class CollClient {

public static void main(String ... sss) {HashSet myMap = new HashSet();String s1 = new String("das");String s2 = new String("das");

NameBean s3 = new NameBean("abcdef");NameBean s4 = new NameBean("abcdef");

myMap.add(s1);myMap.add(s2);myMap.add(s3);myMap.add(s4);

System.out.println(myMap);}

}

optionsA)das abcdef abcdefB)das das abcdef abcdefC)das abcdefD)abcdef abcdef


Explanations : Need to implement 'equals' and 'hashCode' methods to get unique Set for user defind objects(NameBean).

String object internally implements 'equals' and 'hashCode' methods therefore Set only stored one value.Questions no -27 Synchronized resizable-array implementation of the List interface is _____________?

optionsA)Vector

B)ArrayListC)HashtableD)HashMap


Explanations : Vector implements List, RandomAccess - Synchronized resizable-array implementation of the List interface with additional "legacy methods."Questions no -28 What is the output for the below code ?public class Test {

public static void main(String argv[]){ ArrayList list = new ArrayList(); ArrayList<String> listStr = list; ArrayList<StringBuffer> listBuf = list; listStr.add(0, "Hello"); StringBuffer buff = listBuf.get(0); System.out.println(buff.toString()); }

}

optionsA)HelloB)Compile errorC)java.lang.ClassCastExceptionD)null


Explanations : java.lang.String cannot be cast to java.lang.StringBuffer at the code StringBuffer buff = listBuf.get(0); So thows java.lang.ClassCastException.Questions no -29 What is the output for the below code ?

import java.util.LinkedList;import java.util.Queue;


Queue<String> q = new LinkedList<String>(); q.add("newyork"); q.add("ca"); q.add("texas");

show(q); }

public static void show(Queue q) { q.add(new Integer(11)); while (!q.isEmpty ( ) ) System.out.print(q.poll() + " "); }

}

optionsA)Compile error : Integer can't addB)newyork ca texas 11C)newyork ca texasD)newyork ca


Explanations : q was originally declared as Queue<String>, But in show() method it is passed as an untyped Queue. nothing in the compiler or JVM prevents us from adding an Integer after that. If the show method signature is public static void show(Queue<String> q) than you can't add Integer, Only String allowed. But public static void show(Queue q) is untyped Queue so you can add Integer. poll() Retrieves and removes the head of this queue, or returns null if this queue is empty.Questions no -30 What is the output for the below code ?

public interface TestInf { int i =10;}


TestInf.i=12;System.out.println(TestInf.i);

}

}

optionsA)Compile with errorB)10

C)12D) Runtime Exception


Explanations : All the variables declared in interface is Implicitly static and final , therefore can't change the value.Questions no -31 What is the output for the below code ?

public class Test { static { int a = 5; } public static void main(String[] args){ System.out.println(a); } }

optionsA)Compile with errorB)5C)0D) Runtime Exception


Explanations : A variable declared in a static initialiser is not accessible outside its enclosing block.Questions no -32 What is the output for the below code ?

class A { { System.out.print("b1 "); } public A() { System.out.print("b2 "); }}class B extends A { static { System.out.print("r1 "); } public B() { System.out.print("r2 "); } { System.out.print("r3 "); } static { System.out.print("r4 "); }}class C extends B { public static void main(String[] args) { System.out.print("pre "); new C(); System.out.println("post "); }}

optionsA)r1 r4 pre b1 b2 r3 r2 postB)r1 r4 pre b1 b2 postC)r1 r4 pre b1 b2 post r3 r2

D)pre r1 r4 b1 b2 r2 r3 post


Explanations : All static blocks execute first then blocks and constructor.

Blocks and constructor executes (super class block then super class constructor, sub class block then sub class constructor).

Sequence for static blocks is super class first then sub class.

Sequence for blocks is super class first then sub class.


public class Test {

public static void main(String... args) throws Exception {Integer i = 34;int l = 34;if(i.equals(l)){

System.out.println(true);}else{

System.out.println(false);}

}

}

optionsA)trueB)falseC)Compile ErrorD) Runtime Exception


Explanations : equals() method for the integer wrappers will only return true if the two primitive types and the two values are equal.Questions no -34 Which statement is true about outer class?

optionsA)outer class can only declare public , abstract and finalB)outer class may be privateC)outer class can't be abstractD)outer class can be static


Explanations : outer class can only declare public , abstract and final.Questions no -35


static public class Test {public static void main(String[] args) {

char c = 'a';

switch(c){ case 65: System.out.println("one");break; case 'a': System.out.println("two");break; case 3: System.out.println("three");}

}

}

optionsA)oneB)twoC)Compile error - char can't be permitted in switch statement D)Compile error - Illegal modifier for the class Test; only public, abstract & final are permitted.


Explanations : outer class can only declare public , abstract and final.Illegal modifier for the class Test; only public, abstract & final are permittedQuestions no -36


public class Test {

public static void main(String... args) {ArrayList<Integer> list = new ArrayList<Integer>();list.add(1);list.add(2);list.add(3);

for(int i:list)System.out.println(i);

}}

optionsA)1 2 3B)Compile error , can't add primitive type in ArrayListC)Compile error on for(int i:list) , Incorrect SyntaxD)0 0 0


Explanations : JDK 1.5, 1.6 allows add primitive type in ArrayList and for(int i:list) syntax is also correct.for(int i:list) is same as for(int i=0; i < list.size();i++){

int a = list.get(i);

}Questions no -37 What is the output for the below code ?

public class SuperClass {public int doIt(String str, Integer... data)throws

ArrayIndexOutOfBoundsException{String signature = "(String, Integer[])";System.out.println(str + " " + signature);return 1;

}

}

public class SubClass extends SuperClass{

public int doIt(String str, Integer... data) throws Exception{

String signature = "(String, Integer[])";System.out.println("Overridden: " + str + " " + signature);return 0;

}

public static void main(String... args){

SuperClass sb = new SubClass();try{

sb.doIt("hello", 3);}catch(Exception e){

}

}

}

optionsA)Overridden: hello (String, Integer[])B)hello (String, Integer[])C)This code throws an Exception at RuntimeD)Compile with error


Explanations : Exception Exception is not compatible with throws clause in SuperClass.doIt(String, Integer[]). The same exception or subclass of that exception is allowed.

Questions no -38What is the result of executing the following code, using the parameters 0 and 3 ?

public void divide(int a, int b) {try {

int c = a / b;} catch (Exception e) {

System.out.print("Exception ");} finally {

System.out.println("Finally");}

optionsA)Prints out: Exception FinallyB)Prints out: FinallyC)Prints out: ExceptionD)Compile with error


Explanations : finally block always executed whether exception occurs or not. 0/3 = 0 Does not throws exception.

Questions no -39Which of the below statement is true about Error?

optionsA)An Error is a subclass of ThrowableB)An Error is a subclass of ExceptionC)Error indicates serious problems that a reasonable application should not try to catch.D)An Error is a subclass of IOException

Correct answer is : A and C

Explanations : An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch.Questions no -40

Which of the following is type of RuntimeException?

optionsA)IOExceptionB)ArrayIndexOutOfBoundsExceptionC)ExceptionD)Error


Explanations : Below is the tree.java.lang.Object java.lang.Throwable java.lang.Exception java.lang.RuntimeException java.lang.IndexOutOfBoundsException java.lang.ArrayIndexOutOfBoundsExceptionQuestions no -41 What is the output for the below code ?

public class Test {

public static void main(String... args) throws Exception { File file = new File("test.txt"); System.out.println(file.exists()); FileWriter fw = new FileWriter(file); System.out.println(file.exists());

}

}

optionsA)true trueB)false falseC)false trueD)true false


Explanations :Creating a new instance of the class File, you're not yet making an actual file, you're just creating a filename.

So file.exists() return false.

FileWriter fw = new FileWriter(file) do three things:

It created a FileWriter reference variable fw.

It created a FileWriter object, and assigned it to fw.

It created an actual empty file out on the disk.

So file.exists() return true.Questions no -42 When comparing java.io.BufferedWriter and java.io.FileWriter, which capability exist as a method in only one of two ?

optionsA)closing the streamB)flushing the streamC)writting to the streamD)writting a line separator to the stream


Explanations :A newLine() method is provided in BufferedWriter which is not in FileWriter.Questions no -43 What is the output for the below code ?public class Test{

public static void main(String[] args) { int i1=1; switch(i1){ case 1: System.out.println("one"); case 2: System.out.println("two"); case 3: System.out.println("three");}}}

optionsA)one two threeB)oneC)one twoD)Compile error.


Explanations : There is no break statement in case 1 so it causes the below case statements to execute regardless of their values.Questions no -44 What is the output for the below code ?public class Test {

public static void main(String[] args) { char c = 'a';

switch(c){ case 65: System.out.println("one");break; case 'a': System.out.println("two");break; case 3: System.out.println("three");}

}

}

optionsA)one two threeB)oneC)twoD)Compile error - char can't be in switch statement.


Explanations : Compile properly and print two.Questions no -45 What is the output for the below code ?

import java.util.NavigableMap;import java.util.concurrent.ConcurrentSkipListMap;


NavigableMap <Integer, String>navMap = new ConcurrentSkipListMap<Integer, String>();

navMap.put(4, "April");navMap.put(5, "May");navMap.put(6, "June");navMap.put(1, "January");navMap.put(2, "February");navMap.put(3, "March");

navMap.pollFirstEntry(); navMap.pollLastEntry(); navMap.pollFirstEntry(); System.out.println(navMap.size());

}

}

optionsA)Compile error : No method name like pollFirstEntry() or pollLastEntry()B)3C)6D)4


Explanations : pollFirstEntry() Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty.

pollLastEntry() Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.Questions no -46What is the output for the below code ?



NavigableMap <Integer, String>navMap = new ConcurrentSkipListMap<Integer, String>();

System.out.print(navMap.lastEntry());

}

}

optionsA)Compile error : No method name like lastEntry()B)nullC)NullPointerExceptionD)0


Explanations : lastEntry() Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.Questions no -47What is the output for the below code ?



NavigableMap<Integer, String>navMap = new ConcurrentSkipListMap<Integer, String>();

navMap.put(4, "April");navMap.put(5, "May");navMap.put(6, "June");navMap.put(1, "January");navMap.put(2, "February");

System.out.print(navMap.ceilingKey(3));

}

}

optionsA)Compile error : No method name like ceilingKey()B)nullC)NullPointerExceptionD)4


Explanations : Returns the least key greater than or equal to the given key, or null if there is no such key.

In the above case : 3 is not a key so return 4 (least key greater than or equal to the given key).Questions no -48What is the output for the below code ?



NavigableMap<Integer, String>navMap = new ConcurrentSkipListMap<Integer, String>();

navMap.put(4, "April");navMap.put(5, "May");navMap.put(6, "June");navMap.put(1, "January");

navMap.put(2, "February");

System.out.print(navMap.floorKey(3));

}

}

optionsA)Compile error : No method name like floorKey()B)nullC)NullPointerExceptionD)2


Explanations : Returns the greatest key less than or equal to the given key, or null if there is no such key.

In the above case : 3 is not a key so return 2 (greatest key less than or equal to the given key).Questions no -49 What is the output for the below code ?


List<Integer> lst = new ArrayList<Integer>(); lst.add(34); lst.add(6); lst.add(6); lst.add(6); lst.add(6); lst.add(5);

NavigableSet<Integer> nvset = new TreeSet(lst); System.out.println(nvset.tailSet(6)); }

}

optionsA)Compile error : No method name like tailSet()B)6 34C)5D)5 6 34


Explanations : tailSet(6) Returns elements are greater than or equal to 6.Questions no -50 What is the output for the below code ?

import java.util.ArrayList;import java.util.List;import java.util.NavigableSet;import java.util.TreeSet;


List<Integer> lst = new ArrayList<Integer>(); lst.add(34); lst.add(6); lst.add(6); lst.add(6); lst.add(6);

NavigableSet<Integer> nvset = new TreeSet(lst); nvset.pollFirst(); nvset.pollLast();

System.out.println(nvset.size());

}

}

optionsA)Compile error : No method name like pollFirst() or pollLast()B)0C)3D)5


Explanations : pollFirst() Retrieves and removes the first (lowest) element, or returns null if this set is empty.

pollLast() Retrieves and removes the last (highest) element, or returns null if this set is empty.

Questions no -51What is the output for the below code ?

import java.util.ArrayList;import java.util.List;import java.util.NavigableSet;import java.util.TreeSet;


List<Integer> lst = new ArrayList<Integer>(); lst.add(34); lst.add(6); lst.add(2); lst.add(8);

lst.add(7); lst.add(10); NavigableSet<Integer> nvset = new TreeSet(lst); System.out.println(nvset.lower(6)+" "+nvset.higher(6)+ " "+

nvset.lower(2)); }

}

optionsA)1 2 7 10 34 nullB)2 7 nullC)2 7 34D)1 2 7 10 34


Explanations : lower() Returns the greatest element in this set strictly less than the given element, or null if there is no such element.

higher() Returns the least element in this set strictly greater than the given element, or null if there is no such element.

Questions no -52What is the output for the below code ?

import java.util.ArrayList;import java.util.Iterator;import java.util.List;import java.util.NavigableSet;import java.util.TreeSet;


List<Integer> lst = new ArrayList<Integer>(); lst.add(34); lst.add(6); lst.add(2); lst.add(8);

lst.add(7); lst.add(10); NavigableSet<Integer> nvset = new TreeSet(lst); System.out.println(nvset.headSet(10));

}

}

optionsA)Compile error : No method name like headSet()B)2, 6, 7, 8, 10C)2, 6, 7, 8D)34


Explanations : headSet(10) Returns the elements elements are strictly less than 10.

headSet(10,false) Returns the elements elements are strictly less than 10.

headSet(10,true) Returns the elements elements are strictly less than or equal to 10.


import java.io.Console;


Console con = System.console(); boolean auth = false; if (con != null) { int count = 0; do { String uname = con.readLine(null);

char[] pwd = con.readPassword("Enter %s's password: ", uname);

con.writer().write("\n\n"); } while (!auth && ++count < 3); }

}

}

optionsA)NullPointerExceptionB)It works properlyC)Compile Error : No readPassword() method in Console class.D)null


Explanations : passing a null argument to any method in Console class will cause a NullPointerException to be thrown.

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