Question

Explain the difference between Arrays and ArrayList. What are the limitation of arrays? How many primitive data types Java have? Please list them out and list the corresponding wrapper classes for each type. What is the different between String class and StringBuilder class?

Answer 1

Solution :

Q. DIFFERENCE BETWEEN ARRAY AND ARRAYLIST

Array is a fixed length data structure, that is once declared we cannot change the length of the array later while ArrayList is a part of a collection framework which is present in the package of java (java.util). It resizes itself when the capacity gets full.

If we try to store type which is not convertible into type of array, Array throws an exception. Thus we cannot use Generics along with array while ArrayList allows us to use Generics to overcome this disadvantage.

It is mandatory to specify the size of the array while we can create an ArrayList with a default value of 10 and increase it later.

Array can store both primitive data types as well as objects of a class while ArrayList can store only objects and not primitive datas

Arrays can be multi-dimensional while ArrayLIsts are always single dimensional

Q.LIMITATION OF ARRAYS

1. Array is static in nature. Hence once the size is specified it cannot be changed later on.
2. Array occupies contiguous memory location hence scattered memory locations cannot be used in case we are to use an array of big size.
3. The time complexity increases during insertion and deletion operations

Q.LIST OUT THE DIFFERENT PRIMITIVE DATATYPES AND THEIR CORRESPONDING WRAPPER CLASS

There are 8 primitive data types in JAVA,

1. bool - its size is 1 bit. Its corresponding class is Boolean
2. byte - its size is 8 bits. Its corresponding class is Byte
3. char - its size is 16 bits. Its corresponding class is Character
4. short - its size is 16 bits. Its corresponding class is Short
5. int - its size is 32 bits. Its corresponding class is Integer
6. long - its size is 64 bits. Its corresponding class is Long
7. float - its size is 32 bits. Its corresponding class is Float
8. double - its size is 64 bits. Its corresponding class is Double

Q. DIFFERENCE BETWEEN STRING CLASS AND STRINGBUILDER CLASS

1. String is immutable in nature while StringBuilder is mutable.
2. It is thread safe while StringBuilder is not.
3. Strings are used when we dont have to change the input much while StringBuilder is used0 when its going to change often with single thread