Arrays and Arraylist
1. Collection of similar types.
2.Allocated memory at run time and of fixed size .
3.Arrays created using new are initiated with 0 for numeric types(including char), false (for boolean types ) and array of objects are initiazed with null .
1.An array with dynamic length .
2.It maintains an array internally and whenever that becomes small or inefficient it copies those elements into a new bigger array .
3.Arraylist class is a generic class .You have to specify what kind of arraylist we want , whether string or integer .
4.When you initially create a arraylist its size is zero
5.Now when you do
Its length gets increased to 2 .
6.You can add or remove elements anywhere in the arraylist .
friends.remove(0);//removes based on syntax
friends.add(0,"paul");//adding based on index ..adds before index zero
friends.set(1,"harry");//replaces an element
friends.get(0);//retrieves an element based on index
friends.size();//returns size/length of arraylist
7.You cannot have an ArrayList of primitive types .
8.Automatic conversion from primitive types to its object type is called autoboxing . This happens when you add int to a ArrayList of Integer .
9. Be careful while comparing elements if Arraylist using == and != they compare the object reference and not contents of the object . You should first unbox them using automatic inbox by holding them into their primitive types and them comparing them
It is a dynamically created object that hold values of same type.The variables in the array are ordered and each have an index beginning from 0 . Arrays are useful when executing calculations within a loop. The size of an array must be specified by an int value. The direct super class of array type is Object.
Valid declaration syntax are
EG: int boxes OR
To access the first element we use boxes;
Arraylist is a resizable array, can be found in java.util package. It is helpful in programs where lots of manipulation in the array is needed . Java ArrayList allows us to randomly access the list.
Can you give me summary of java collections framework ?