In this pots i will explain some methods of ArrayList.
1)clone:This method is used to make a exact copy of list.This method returns object so we need to add casting to it.
Suppose list is an ArrayList and we have added some elements to it.
ArrayList<String> list=new ArrayList<String>();
list.add("First List");
list.add(1,...
Thursday, 12 March 2015
ArrayList Methods in Java
In this method i will explain some methods of ArrayList which are used frequently.
1)ensureCapacity():This method is used to increase the size of the ArrayList,if necessary to ensure that it can hold at least the number of elements specified by the minimum capacity argument.
list.ensureCapacity(30);
By above...
Tuesday, 10 March 2015
ArrayList in Java
Java API provides several predefined data structure which are also known as collections in Java.ArrayList is a collection which we can use conveniently in place of array because when we are using array there is a problem that array size cannot be changed automatically at runtime i.e. if we are using an array and it became full then it will throw an...
Arrays Class in Java
In this post i will explain about the Arrays class in Java which is inbuilt and we can use many predefined methods on this Array class which makes our problem simple.
1)sort():This method is used to sort the array elements.
2)equal():This is a method for comparing two arrays.
3)binarySearch():This is a method to find an element using binary search.This...
Java Interview Question-Variable length arguments to method
Do you know that we can pass a variable length argument lists in the method.This can be done by passing the datatype followed by an ellipsis(...) and then variable name.The ellipsis indicates that method can receive variable length of arguments of specific type.We can also use method overloading on this method.The ellipsis passed in the method is...
Monday, 9 March 2015
Array in Java
An array is a group of variables of same types containing some values.In Java Arrays are objects so they are considered reference types.The elements of array can be primitive or reference types.If we want to access any element in the array, then we use the position number of that element in the array.This position number in the array is called the...
Data Hierarchy in Operating Systems
Data an important concept everywhere.Nothing exist without data.If we need to compute anything we need data.If we need to determine any result,we need data.So data is base for all the computing and we this world of computing can't exist without data.What is data in terms of computers, at the lowest level data is stored in the computers in the form...
Thursday, 5 March 2015
Synchronization in Java
What is thread synchronization?
Suppose we have a multi-threaded application i.e. our application have more than one thread.Since we know multiple threads can share an object.Suppose we have an object which is shared by multiple threads because of this unexpected results can occur unless access to shared object is managed properly.For example:We...
Wednesday, 4 March 2015
Typecasting in Java
What is type casting and why do we need it?
Suppose we have a variable of type float and we are assigning it a value of type int then there is no problem since it will automatically converted to float but suppose we have a variable of type int and we are assigning it a value of type double then what will happen? Compiler will throw an error (Type...
Tuesday, 3 March 2015
Concurrency in Java
Every computer user want to do works in a fast way and they also want to do multiple works at a time. Suppose a user is working on MS Paint and now he can't open anything else. Means when he will finish the paint related work after that he can open other applications.Then it will be very bad for user.So to overcome these types of situations concurrency...
Runnable in Java
First question is,What is runnable?
So runnable is an interface which is used to provide concurrency to the application by providing the threads to the application.It is the general way of creating threads.
Why should we use runnable interface over Thread class?
If we use Thread class then we have to create our own threads.We will have to manage...
Monday, 2 March 2015
HashMap in Java
08:17
Collection, Java, Java Interview Questions
No comments
How HashMap works in Java?
It is a simple answer,it works on the principle of hashing.In HashMap elements are stored in pair of (key,value) and also we can fetch the value in constant time O(1) provided we know the key.We store objects in HashMap using put(key,value) and retrieve value using get(key) which returns value.
Working of put(key,value):When...
Reverse of a given number using Java
In this post i will explain how to calculate reverse of the given number.Suppose given number is 234.Then what will be the reverse of this given number?
Answer is 432.
It is easy to find out the reverse of any given number using pen and paper, but if you want to calculate the reverse using a program then how will you write the program.
Lets think...
Star Pattern printing in Java
In this post i will explain about different patterns using java program.
1)Our first pattern is
*
* *
* * *
* * * *
* * * * *
So how can we print this pattern using Java program.First observe this pattern it has five rows and...
Difference between fail-fast and fail-safe iterators
07:57
Collection, Java, Java Interview Questions
No comments
What is the difference between fail-fast and fail-safe iteartors in java?
fail-safe iterator is relatively new concept in comparison to the fail-fast iterator concept.
1)fail-fast iterator:fail-fast iterators fail as soon as they realize that structure of the collection has been modified since iteration has begin.Here structural changes means either...
Sunday, 1 March 2015
Factorial of a number in Java
In this post i will explain how to write a program to get the factorial of a given number.I have written two programs.First one uses for loop to find the factorial and second one uses recursion.But before that i will explain how to find the factorial.
Suppose number is 4.Then to find out factorial of any given number we will multiply it with (number-1)...
Null in Java
null is a very important concept in java.
1) null is not a keyword in java,it is actually a literal just like true and false.
Click here to get a better idea.
2) null is default value for any reference variable in java
static Object obj;
public static void main(String ar[]){
System.out.println("Value of Object is "+obj);
}
Output:...
Final in Java
Final is very important keyword in java which can be applied to variable, method or class in java.Once you make a reference final then you are not allowed to change that reference and on doing so compiler will show the error.
Final variables:We can make the variables final in java and after declaring varibale final we cannot modify it later. Java...
Immutable Objects in Java
Immutable classes are those classes that cannot be modified after creation. If we want to modify immutable class then it will result in new immutable object.Immutable objects are very important in concurrency and they makes the programs efficient.
First we will see how to create an immutable object.As we know there are following step by which any...
Thread concept in java
A thread is known as a lightweight process. A thread is a basic processing unit to which an operating system can allocate processor time.It is better to use threads, but it doesn't mean that we can create as many as threads and our process will become more efficient. But as we know that threads also consume resources so we should create threads according...
