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Java String Handling Test Series 2 | Core Java Topical Test

By Raju Choudhary On Feb 13, 2019

Java String Handling Test | Core Java Topical Test (Series 2)

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Question 1 of 19

1. Question

What is output?

public class Test15{
public static void method(StringBuffer newSb){
newSb.append(” Added”); //Line 3
newSb= new StringBuffer(“Hai”); //Line 4
}
public static void main(String a[]){
StringBuffer sb = new StringBuffer(“String Buffer”);
method(sb);
System.out.println(sb);
}
}

Choose the one below:

String Buffer Added
Compiler Error
Hai
String Buffer

Correct

As StringBuffer is mutable class when newSb.append(” Added”) is executed, it appends the string value to actual object which is referred by newSb and sb reference variables. At Line 4 new StringBuffer object is created and refrenced by newSb but sb still refer to the actual object and the above code snippet results to “String Buffer Added“.

Incorrect

Question 2 of 19

2. Question

What will be the output?

public class Test2{
static void method(String str){
System.out.println(“String”);
}
public static void main(String args[]){
method(null);
}
}

Choose the one below:

null
String
Object
Compiler Error

Correct

static method is associate with class not with object. Hence the above code snippet results “String” as output.

Incorrect

static method is associate with class not with object. Hence the above code snippet results “String” as output.

Question 3 of 19

3. Question
Which of the following methods are methods of the String class?
- delete( )
- reverse( )
- append( )
- replace( )
Correct

replace() method is available in String class and it is returns a new string resulting from replacing all occurrences of old character in this string with new character.

Incorrect

replace() method is available in String class and it is returns a new string resulting from replacing all occurrences of old character in this string with new character.
Question 4 of 19

4. Question
Is String a wrapper class?
- TRUE
- FALSE
Correct

String is not wrapper class. In Java, Wrapper class is defined as class which converts and store equivalet primitive type. For example :- Integer, Character

Incorrect

String is not wrapper class. In Java, Wrapper class is defined as class which converts and store equivalet primitive type. For example :- Integer, Character

Question 5 of 19

5. Question

What will be the output?

System.out.println(“john” == new String(“john”));
System.out.println(“john”.equals(“john”));
System.out.println(“john” == “john”);
System.out.println(new String(“john”)==new String(“john”));

false true false false
false true true true
false true true false
false false true false

Correct

“john” == new String(“john”) produces false as “john” is created in string pool and new String(“john”) at heap and == operator compares object reference.

“john”.equals(“john”) produces true as equals() method compares content of object.

“john” == “john” produces true as “john” is created in String pool and refer to same object.

new String(“john”)==new String(“john”) creates two string in heap and == checks reference of both objects and returns false.

Incorrect

“john” == new String(“john”) produces false as “john” is created in string pool and new String(“john”) at heap and == operator compares object reference.

“john”.equals(“john”) produces true as equals() method compares content of object.

“john” == “john” produces true as “john” is created in String pool and refer to same object.

new String(“john”)==new String(“john”) creates two string in heap and == checks reference of both objects and returns false.

Question 6 of 19

6. Question

Examine the following code

String str = null;
boolean bValue = str instanceof String;

What value is placed in bValue?

TRUE
FALSE
Compile time error

Correct

instanceof is used to check if an object is an instance of a class, an instance of a subclass, or an instance of a class that implements a particular interface. In the above code snippet reference variable str is null. Hence the output is FALSE.

Incorrect

Question 7 of 19

7. Question

What is the output of below code snippet?

if( new String(“ModernPathshala”).trim() == new String(“ModernPathshala”) )
System.out.println(“Equal”);
else
System.out.println(“Not Equal”);

Equal
None of the above
Compile Time Error
Not Equal

Correct

The above code snippet results as Not Equal as an output because reference of both string are not same.

Incorrect

The above code snippet results as Not Equal as an output because reference of both string are not same.

Question 8 of 19

8. Question

What will the following program print when run?

public class Search {
public static void main(String[] args) {
String s = “Contentment!”;
int middle = s.length()/2;
String nt = s.substring(middle-1, middle+1);
System.out.println(s.lastIndexOf(nt, middle));
}
}

Correct

s.length()/2 returns 6
s.substring(middle-1, middle+1) returns nt.
s.lastIndexOf(nt, middle) searches String value “nt” from middle i.e 5th index of String s.
Output:- 5

Incorrect

s.length()/2 returns 6
s.substring(middle-1, middle+1) returns nt.
s.lastIndexOf(nt, middle) searches String value “nt” from middle i.e 5th index of String s.
Output:- 5

Question 9 of 19

9. Question
Which one of the following is not legal?
- System.out.println("st" + "ep");
- System.out.println("st".concat("ep"));
- System.out.println(’s’ + ’t’ + ’e’ + ’p’);
- System.out.println("st" + new String(’e’ + ’p’));
Correct

Option System.out.println(“st” + new String(’e’ + ’p’)); is invalid as ‘e’+’p’ results to an integer value and String class does not have any constructor to create String using integer value.

Incorrect

Option System.out.println(“st” + new String(’e’ + ’p’)); is invalid as ‘e’+’p’ results to an integer value and String class does not have any constructor to create String using integer value.

Question 10 of 19

10. Question

What will be the result of attempting to compile and run the following code?

public class TestStringOperation {
public static void main(String[] args) {
String str1 = new String(“java”);
str1.concat(” world”);
StringBuffer strBuf1 = new StringBuffer(” magazine”);
strBuf1.append(” article”);
System.out.println(str1 + strBuf1);
}
}

The program will print "java world magazine article" when run.
The program will print "world magazine article" when run.
The program will print "java world magazine" when run.
The program will print "java magazine article" when run.

Correct

concat() method returns a new String with the value of the String passed into the methodand append it to the end of the String used to invoke this method. So value of str1 remains “java” after executing str1.concat(” world”); line. Value of strBuf1 becomes “magazine article” after executing strBuf1.append(” article”); line. Hence System.out.println(str1 + strBuf1); results “java magazine article” as an output.

Incorrect

Question 11 of 19

11. Question
What results would print from the following code snippet:
System.out.println(“ABCDE “.valueOf(98765));?
- 98765
- The application won’t compile.
- ABCDE 98765
- Runtime error
Correct

valueOf() is static method defined in String class. Hence the above code compiles and runs successfully and prints 98765 as an output.

Incorrect

valueOf() is static method defined in String class. Hence the above code compiles and runs successfully and prints 98765 as an output.

Question 12 of 19

12. Question

Which one of the expressions will evaluate to true if preceded by the following code?

String a = “hello”;
String b = new String(a);
String c = a;
char[] d = { ‘h’, ‘e’, ‘l’, ‘l’, ‘o’ };

a.equals(d)
(a == "Hello")
a.equals(b)
(a == b)

Correct

a.equals(b) returns true as equals() method compares content of two string if same or not.

Incorrect

a.equals(b) returns true as equals() method compares content of two string if same or not.

Question 13 of 19

13. Question

What will be the result of attempting to compile and run the following program?

public class MyClass {
public static void main(String[] args) {
StringBuffer sb = new StringBuffer(“have a nice day“);
sb.setLength(6);
System.out.println(sb);
}
}

The program will throw a StringIndexOutOfBoundsException when run.
The program will print "have a" when run.
The program will print "ce day" when run.
The code will fail to compile since there is no method named setLength in the StringBuffer class.

Correct

The program will print “have a” when run.

Incorrect

The program will print “have a” when run.

Question 14 of 19

14. Question

What will be written to the standard output when the following program is run?

import static java.lang.System.out;
public class TestOutput {
public static void main(String[] args) {
String space = ” “;
String composite = space + “windows” + space + space;
composite.concat(“server”);
String trimmed = composite.trim();
out.println(trimmed.length());
}
}

Correct

concat() method returns a String with the value of the String passed into the methodand append it to the end of the String used to invoke this method. Hence the value of composite does not change.

Incorrect

concat() method returns a String with the value of the String passed into the methodand append it to the end of the String used to invoke this method. Hence the value of composite does not change.

Question 15 of 19

15. Question

What is the output for following code snippet?

String string = “null”+null+“null”;
System.out.println(string);

nullnull
Null Pointer Exception at Runtime
nullnullnull
Compile Time Exception

Correct

In java String class if String reference is null, it is converted to the string “null”.

Hence the above code returns nullnullnull as an output.

Incorrect

In java String class if String reference is null, it is converted to the string “null”.

Hence the above code returns nullnullnull as an output.

Question 16 of 19

16. Question

Given code snippet :-

String str1 = "Modern Pathshala";
String str2 = new String("Modern Pathshala");
String str3 = "Modern Pathshala";

How many objects are created?

2
3
1
None of the above

Correct

In the above code snippet str1 is created in String Pool whereas String created using new operator i.e str2 is created in Heap. Further str3 refers to String Pool object which is already created.

Hence total 2 objects are created.

The pictorial representation of above object creation can be dsescribed as :-

Incorrect

In the above code snippet str1 is created in String Pool whereas String created using new operator i.e str2 is created in Heap. Further str3 refers to String Pool object which is already created.

Hence total 2 objects are created.

The pictorial representation of above object creation can be dsescribed as :-

Question 17 of 19

17. Question

What is the output of below code snippet?

System.out.println((“a” + “b” + “c”).intern() == “abc”);

true
false

Correct

The Java programming language requires that identical string literals (that is, literals that contain the same sequence of characters) must refer to the same instance of class String. In addition, if the method String.intern is called on any string, the result is a reference to the same class instance that would be returned if that string appeared as a literal. Thus,

(“a” + “b” + “c”).intern() == “abc”

must have the value true.

To derive a string literal, the Java virtual machine examines the sequence of characters given by the CONSTANT_String_info structure.

If the method String.intern has previously been called on an instance of class String containing a sequence of Unicode characters identical to that given by the CONSTANT_String_info structure, then the result of string literal derivation is a reference to that same instance of class String.
Otherwise, a new instance of class String is created containing the sequence of Unicode characters given by the CONSTANT_String_info structure; that class instance is the result of string literal derivation. Finally, the intern method of the new String instance is invoked.

Incorrect

(“a” + “b” + “c”).intern() == “abc”

must have the value true.

To derive a string literal, the Java virtual machine examines the sequence of characters given by the CONSTANT_String_info structure.

If the method String.intern has previously been called on an instance of class String containing a sequence of Unicode characters identical to that given by the CONSTANT_String_info structure, then the result of string literal derivation is a reference to that same instance of class String.
Otherwise, a new instance of class String is created containing the sequence of Unicode characters given by the CONSTANT_String_info structure; that class instance is the result of string literal derivation. Finally, the intern method of the new String instance is invoked.

Question 18 of 19

18. Question

Given code snippet :-

String s;
int a;
s = “Foolish boy.”;
a = s.indexOf(“fool”);

What is the output?

-1
0
4
random value

Correct

Incorrect

Question 19 of 19

19. Question

Identify error in below source code –

public class JavaStringIsEmpty
{
public static void main(String args[])
{
String strl = “”;
String str2 = null;
String str2 = “Hello Java”;
System.out.println(“Is String 1 empty? :” + strl.isEmpty());
System.out.println(“Is String 3 empty? :” + str3.isEmpty());
}
}

No error
String str2 = "Hello Java";
public static void main(String args[]){
System.out.println("Is String 1 empty? :" + str1.isEmpty());

Correct

Same variable str2 is declared twice which is not allowed.

Incorrect

Same variable str2 is declared twice which is not allowed.

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Java String Handling Test Series 2 | Core Java Topical Test

Java String Handling Test | Core Java Topical Test (Series 2)

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