MCQ Based questions for CUET Information practice (IP) Chapter 12 More about classes and libraries

(c)

Explanation : A package is a group of logically related classes which make the feature of reusability easier to accomplish. It is like a container for classes and can be accessed in any program.

(b)

Explanation : Accessor methods are the methods used to obtain information about an object. The String class provides various accessor methods that may be used to perform operations on strings. Some Accessor methods are capacity(),charAt(), compareTo(), concat() etc.

(c)

Explanation : Access Specifier determines which feature of a class (the class itself, data members ,member functions) may be used by other class. It controls the access to methods and fields. There are four types of access specifier in java – Public, protected, private and default.

(d)

Explanation : In inheritance, a class can inherit the properties from another class. The inheriting class is a subclass or derived class and the class being inherited is a superclass or base class.

(d)

Explanation : The methods and fields of a class declared with static are also known as class fields and class methods. Static members belong to a class as a whole and not to a particular instance (object).

(c)

Explanation : A set of readymade software routines (class definitions) that can be reused in new program is called a Library. Java offers many libraries that the programmers can use as per their needs. There are numerous java libraries pertaining to different functions such as user interface libraries, XML libraries, database connectivity libraries and many others.

(a)

Explanation : “java.lang” contain language support classes. These classes are used by java compiler itself; therefore, they are automatically or by default imported into the program of java.

(d)

Explanation : Instances or objects of StringBuffer class can hold mutable strings that can be changed or modified.

(c)

Explanation : The instances or objects of a character can hold single character data. This class offers many methods to manipulate or inspect single-character data.

(c)

Explanation : Libraries are generally imported or used in a program by using IMPORT statement.

To import java’s IO (java.io) library, you will write:

import java.io.*

(a)

Explanation : To perform mathematical computation in the program, java has provided MATH library which contains a set of useful mathematical functions and constants. Math library is available in “java.util” package. To use Math library you need to import “java.util” package.

(b)

Explanation : To compute something in the form a^b where a and b are numbers, we can use pow() method of MATH library.

Syntax:

pow (double a , double b)

It returns the first argument (a here) raised to the power of the second argument (b here), i.e., a^b.

(b)

Explanation : All input and output related classes are part of “java.io” package. Here “io” stands for Input/Output.

(c)

Explanation : As an object oriented language each and everything in java is considered as an object. Every class has an Object as a superclass.

(a)

Explanation : Calendar class is the part of “java.util” package. This class is an abstract class whose object is created with the help of following method:

Static calendar getInstance();

Calendar Calcurrent = Calendar.getInstance();

These statements create a Calendar object namely Calcurrent

(d)

Explanation : Java is an object oriented language. Strings are also handled as objects and one advantage of it is that a string object has a great variety of methods that we can use with it.

(a)

Explanation : The String class object can hold unchanging(immutable) string, i.e., once initialized its contents cannot be modified.

(d)

Explanation : In object oriented language, classes are used to bind methods and variables in one single unit.

(a)

Explanation : The CLASSPATH is an environment variable that tells the Java compiler where to find the compiled bytecode files. The CLASSPATH is either defined for the file you create and the one required by the system that comes with the JDK itself. So, we always need to set the classpath.

(d)

Explanation : If no access specifier is used, then the class member has default access, i.e., known as default access specifier. Members with default access are available to all classes in the same package, but are not available to any classes in other packages, even subclasses. It is also termed as friendly or package access.

(a)

Exp: To create user defined package we need to declare the name of the package followed by the package keyword at the beginning of a file using the form:

Package World;

//World is the name of the package.

(b)

Explanation : Inheritance is the property through which we can control the access to the class members, i.e., fields as well as methods. So, it is helpful in enforcing information hiding.

(b)

Explanation : Date class is used to show the specific instant of time. This class is available in “java.util” package so to use it we need to import “java.util.Date” package using import statement.

(a)

Explanation : Calendar is an abstract base class for converting between a Date object and a set of integer fields such as YEAR, MONTH, DAY, HOUR and so on.

(b)

Explanation : To create a java.util.Calendar object, you have to use its static getInstance method:

Static Calendar getInstance( );

Calendar calCurrent =Calendar.getInstance( );

Above statements create a Calendar object namely calCurrent.

(c)

Explanation: The Calendar object can set/get values for day, month, year, hour, minute, second, day of the week etc using one of the following two overloaded method:

set(int field, int value);

get(int field);

get() method is used to obtain value of specific field.

(c)

Explanation: The networking related classes are defined in “java.net” package. So to use these classes we have to use “import” statement as follows:

import java.net.*;

(c)

Explanation : There are two types of package available in java:

a) Java API package

b) User-defined package

Java API (Application Programming Interface) package provides a large number of classes grouped into different packages according to functionality. It is system defined package whereas user defined packages are created by users.

(c)

Explanation : NaN is a way to express Not-A-Number in java. If any argument is not a number, i.e., NaN^6, then the result is a NaN.

(b)

Explanation : If we use setLength() method to specify a length shorter than its String, then the string is truncated.

(c)

Explanation: pow() and round() methods are defined in Math class which is the part of java.lang package. pow() method is used to find the power of number in the form a^b and round() method round off a number to its nearest integer.

(d)

Explanation : The public members are visible to the entire class in which it is defined. Public access Specifier Specify that all the methods and variable are directly accessible from all other classes.

(d)

Explanation : StringBuffer class is that class whose instances or objects can hold mutable strings that can be changed or modified.

(c)

Explanation : Some StringBuffer methods return a StringBuffer value like append(), insert() etc. They return the same StringBuffer that was used in the call. This allows chaining of calls.

For example

sb.append(“x= “).append(x).append(“,y=“). append(y);

If x is 5 and y is 2, the above code will give result as x=5,y=2

(b)

Explanation : The length() method is an accessor method of String class which returns the length of the current string.

The prototype of length() method is

int length();

(d)

Explanation : The StringBuffer object is more flexible in compare to string object. Stringbuffer object holds mutable string that can be changed or modified whereas a string class object hold immutable string that is of fixed length and cannot be changed.

(b)

Explanation : the prototype of charAt() method is

char charAt(int index)

It returns the character at the specified index.

(b)

Explanation : Protected members can be accessed from within classes belonging to the same package to which the class of protected members belongs.

(c)

Explanation : The dot(.) operator is used to call object methods as follow

Classname obj = new classname();

Obj.method1();

Where obj is the object of classname and method1 is the methods of classname. This method is accessed by using dot(.) operator with the object.

(a)

Explanation : In java“new” operator causes -

Ø a new instance of the given class is created

Ø memory is allocated for it

Ø a constructor is called

A StringBuffer object is always created with the use of new operator as follows:

StringBuffer sf = new StringBuffer;

This method creates an empty stringBuffer object namely sf.

(a)

Explanation : A class is a collection of methods and fields. It binds variables and functions together.

43. Java is a

a. case-sensitive language.

b. procedural language.

c. non-case-sensitive.

d. structured language.

Q.44. The compareTo() method compares two strings

a. linearly.

b. geometrically.

c. lexicographically.

d. geographically.

Q.45. Lexicography is the way of writing words in

a. non-alphabetical order.

b. small letter.

c. alphabetical order.

d. capital letter.

Q.46. Character class is a

a. Wrapper class.

b. Inherited class.

c. Package of classes.

d. Library of methods.

Q.47. For creating an object, it is mandatory to use “new” operator in

a. StringBuffer class.

b. String class.

c. Object class.

d. Character class.

Q.48. The class member that restricts accessibility in subclasses

a. public.

b. protected.

c. private.

d. default.

Q.49. To concatenate two strings, we can use

a. capacity() method.

b. charAt() method.

c. valueOf() method.

d. Concat() method.

Q.50. The method used to calculate absolute value of a number

a. abs() method.

b. absolute() method.

c. value() method.

d. floor() method.

Q.51. The keyword used to represent current string is

a. that.

b. object.

c. current.

d. this.

Q.52. The method that is used to remove white spaces from both ends of the string is

a. truncate().

b. remove().

c. trim().

d. hide().

Q.53. To return a new string from the current string we can use

a. “+” operator.

b. substring() method.

c. Trim() method.

d. “-” operator.

Q.54. The operator that is alternative to concat() method is

a. “/” operator.

b. “-” operator.

c. “+” operator.

d. “\” operator.

Q.55. A string object encapsulates sequence of

a. operators.

b. methods.

c. texts.

d. characters.

Q.56. The method that compares strings while ignoring case is

a. compareTo().

b. equalsIgnoreCase().

c. compareIgnoreCase().

d. equalsCompareCase().

Q.57. A StringBuffer object contains a memory block called

a. Memory.

b. Buffer.

c. Cache.

d. Block.

Q.58. When the StringBuffer object’s length is longer than the String it holds, the extra character contains

a. ’\u0000’.

b. ’\f0000’.

c. ’\a0000’.

d. ’\g0000’.

Q.59. You can change the length of a string in a StringBuffer object with the

a. get() method.

b. length() method.

c. set() method.

d. setLength() method.

Q.60. StringBuffer sf = new StringBuffer;

This method creates a “sf” string object of

a. full length.

b. empty length.

c. null length.

d. full capacity.

Q.61. In StringBuffer class “append()” and “insert()” methods are overloaded and will call the

a. toChar() method for all objects.

b. String() method for all objects.

c. StringBuffer() method for all objects.

d. toString() method for all objects.

Q.62. Math.round(-1.5 will yield the result as an E-mail application is a type of

a. 1.

b. -2.

c. -1

d. 1.5.

Ans : c.

Explanation : “round()” method add 0.5 to the argument and returns the closest integer/long value

Math.round(-1.5)

will yield the result as -1

(a)

Explanation : If the argument is not a number in round() methods it will return ZERO.

Math.round(Float.NaN)

will return zero(0)

(b)

Explanation : If the argument is a negative infinity or less than the MIN_VALUE for the type, then it will return the MIN_VALUE of the return type

Math.round(Float.NEGATIVE_INFINITY)

will return -2147483648

-2147483648 is the minimum value of the integer data type in java.

(c)

Explanation : API stands for Application Programming Interface. Java API is the collection of system packages that we can import in our java program.

(b)

Explanation : Two classes in two different packages can have the same name. In packages, classes can be unique compared with classes in other packages, i.e., two classes in two different packages can have the same name.

(a)

Explanation : Packages are java’s way of grouping a variety of classes and/or interfaces together. It act as ”containers” for classes.

(a)

Explanation : If the argument is a positive infinity or greater than the MAX_VALUE for the type, then it will return the MAX_VALUE of the return type.

Math.round(Float.POSITIVE_INFINITY)

will return 9223372036854775807

9223372036854775807 is the maximum value of the long data type in java.

(d)

Explanation : The packages are organized in a hierarchical structure. The package named java contains the package awt, which in turn contains various classes required for implementing graphical user interface.

(c)

Explanation : The defined classes in a user defined package need to be declared with public access specifier. It is always created to get used in other programs so we need to declare the classes with public access-specifier.

(a)

Explanation : If we compile a file of a user defined package, it will create a “.class” file.

(d)

Explanation : java.util.Calendar class is used to Convert a Date field to integer field. Calendar is an abstract base class for converting between a Date object and a set of integer fields such as YEAR, MONTH, DAY, HOUR and so on.

(a)

Explanation : java.util.Date class is used to represents a date objects in a long integer format. A Date object represents a specific instant in time.

(b)

Explanation : To create a java.util.Calendar object, you have to use its static getInstance method as follows:

Static Calendar getInstance( );

Calendar calCurrent =Calendar.getInstance( );

These statements create a Calendar object namely calCurrent

(d)

Explanation : The Calendar class provides some static int fields.

Calendar.DATE field is used to store numeric date.

(b)

Explanation : The public members are accessed through dot(.) operator as follows

Obj.mathodname();

Obj is an object used to access a method, i.e., methodname.

(a)

Explanation : “capacity()” is an accessor method of String class that returns the maximum number of characters that can be entered in the current string object. The prototype of capacity() method is

int capacity();

(d)

Explanation : If the argument passed is Float.MAX_VALUE, the round() method returns integer.MAX_VALUE.

Math.round(Float.MAX_VALUE)

will return 2147483648

2147483648 is the maximum value of the integer data type in java.

(d)

Explanation : “replace()”is the method of string class whereas the other three methods are of StringBuffer class.

The prototype of replace() method is

String replace(char oidChar, char newChar)

It returns a new string resulting from replacing all occurrences of “oldChar” in the current string with the “newChar”.

(c)

Explanation : The declaration of a method is also known as Method Prototype. The syntax of method declaration is as follows:

Return-type Method-name (Parameter list)

{

//Body of the method;

}