Question

What is the difference between the String class and the StringBuilder class in the API? Group of answer choices they are in different packages a String can only contain letters while a StringBuilder can contain any character a String is immutable and a StringBuilder is mutable there is no difference A class can directly extend many classes. Group of answer choices True False With this declaration: Student s1; What possible values can s1 hold? Group of answer choices с a Student object a String the address of a Student object the address of any object

Answer 1

Yes, Option a String is immutable and a StringBulider is mutable is Correct Option.

The String and StringBulider both are in same package called Java.lang, so Option they are in different packages is Incorrect Option.

String is type of array which contains charcters as letters and StringBulider does the same. So Option a string can only contain letters while a StringBuilder can contain any character is Incorrect Option.

As you seen there is difference String and StringBuilder so, Option there is no difference is Incorrect Option.

Yes, Option False is Correct Option.

In question A class can directly extend many classes,the extend(extends in java programming) keyword extends a class indicate that one class inherited from another class.

You can only directly extend one class because Java does not support Multiple inheritance. However in Java multiple inheritance possible through interfaces only. A class can implement any number of interfaces but can extend only one class.

Yes, Option the address of Student object is Correct Option.

With this declartion
Student s1;

Here Student is not a any type of Data type.So we can not write it directly as variable member.It must be in a class Student in which Student s1 will be link Address or reference as s1 of Student class.In this way s1 hold the address of Student Object.

Please refer this code image for better approach:

public class Student { Student sl; //link Address or reference as sl of Student class }

We aren't using object when we assign an object to variable so it is just the address of Student Object not only Student Object. So Option a Student object is Incorrect Option.

As you can see this is not any data type so it will not a String,So Option a String is Incorrect Option.

It can not be address of any Object it will be address of Student class only, So Option the address of any object is Incorrect Option.