Java String Basics

String Handling

    1) Which package does define String and StringBuffer classes?

        Ans : java.lang package.

    2) Which method can be used to obtain the length of the String?

        Ans : length( ) method.

    3) How do you concatenate Strings?

        Ans : By using ” + ” operator.

    4) Which method can be used to compare two strings for equality?

        Ans : equals( ) method.

    5) Which method can be used to perform a comparison between strings that ignores case differences?

        Ans : equalsIgnoreCase( ) method.

    6) What is the use of valueOf( ) method?

        Ans : valueOf( ) method converts data from its internal format into a human-readable form.

    7) What are the uses of toLowerCase( ) and toUpperCase( ) methods?

        Ans : The method toLowerCase( ) converts all the characters in a string from uppercase to

        lowercase.

        The method toUpperCase( ) converts all the characters in a string from lowercase to

        uppercase.

    8) Which method can be used to find out the total allocated capacity of a StrinBuffer?

        Ans : capacity( ) method.

    9) Which method can be used to set the length of the buffer within a StringBuffer object?

        Ans : setLength( ).

    10) What is the difference between String and StringBuffer?

        Ans : String objects are constants, whereas StringBuffer objects are not.

        String class supports constant strings, whereas StringBuffer class supports growable, modifiable strings.

    11) What are wrapper classes?

        Ans : Wrapper classes are classes that allow primitive types to be accessed as objects.

    12) Which of the following is not a wrapper class?

            String
            Integer
            Boolean
            Character

        Ans : a.

    13) What is the output of the following program?

    public class Question {

    public static void main(String args[]) {

    String s1 = “abc”;

    String s2 = “def”;

    String s3 = s1.concat(s2.toUpperCase( ) );

    System.out.println(s1+s2+s3);

    }

    }

            abcdefabcdef
            abcabcDEFDEF
            abcdefabcDEF
            None of the above

        ANS : c.

    14) Which of the following methods are methods of the String class?

            delete( )
            append( )
            reverse( )
            replace( )

        Ans : d.

    15) Which of the following methods cause the String object referenced by s to be changed?

            s.concat( )
            s.toUpperCase( )
            s.replace( )
            s.valueOf( )

        Ans : a and b.

    16) String is a wrapper class?

            True
            False

        Ans : b.

    17) If you run the code below, what gets printed out?

    String s=new String(“Bicycle”);

    int iBegin=1;

    char iEnd=3;

    System.out.println(s.substring(iBegin,iEnd));

            Bic
            ic
            icy
            error: no method matching substring(int,char)

        Ans : b.

    18) Given the following declarations

    String s1=new String(“Hello”)

    String s2=new String(“there”);

    String s3=new String();

    Which of the following are legal operations?

            s3=s1 + s2;
            s3=s1 – s2;
            s3=s1 & s2
            s3=s1 && s2

        Ans : a.

    19) Which of the following statements are true?

        a)The String class is implemented as a char array, elements are addressed using the stringname[] convention

        b) Strings are a primitive type in Java that overloads the + operator for concatenation

        c) Strings are a primitive type in Java and the StringBuffer is used as the matching wrapper type

        d) The size of a string can be retrieved using the length property.

        Ans : b.