How to Convert Enumeration to Arraylist - Java Example

We can convert enumeration to arraylist in java with  the help list() method of Collections.

package javaproficeincy;

import java.util.Collections;

import java.util.Enumeration;

import java.util.List;

import java.util.Vector;

public class EnumerationToList {

public static void main(String[] args) {

Vector<String> vt = new Vector<String>();

        vt.add("java");

        vt.add("php");

        vt.add("array");

        vt.add("string");

        vt.add("c");

        Enumeration<String> enm = vt.elements();

        List<String> ll = Collections.list(enm);

        System.out.println("List elements: "+ll);

}

}

Output:

List elements: [java, php, array, string, c]

Related Posts :

How to Send message from one user to other ( chat example) In xmpp

We have knew how to add roster in xmpp server . Now we will send message from one user to other.
There is simple example for creating chat. There we will send a message using smack api and xmpp server. You can can visit how to install xmpp server.

package com.javaproficiency.demo;

import java.util.Collection;

import org.jivesoftware.smack.Chat;
import org.jivesoftware.smack.ConnectionConfiguration;
import org.jivesoftware.smack.MessageListener;
import org.jivesoftware.smack.Roster;
import org.jivesoftware.smack.RosterEntry;
import org.jivesoftware.smack.XMPPConnection;
import org.jivesoftware.smack.XMPPException;
import org.jivesoftware.smack.packet.Message;



public class SendMessageInChat {

 public static void main(String[] args) {

   AddRoster addRoster = new AddRoster();
 
XMPPConnection connection = addRoster.Connect();
try {
connection.login("yogesh@localhost","123");
System.out.println("Login");

Chat chat = connection.getChatManager().createChat("shivam@localhost", new MessageListener() {

@Override
            public void processMessage(Chat chat, Message message) {
                // Print out any messages we get back to standard out.
                System.out.println("Received message: " + message);
            }

        });
        try {
chat.sendMessage("How are you dear !!");
System.out.println(" Send Message succesfully");
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

           connection.disconnect();

} catch (XMPPException e) {

e.printStackTrace();
}
}


private void loginUser(XMPPConnection connection) {
// TODO Auto-generated method stub

}


public XMPPConnection Connect() {
 
  ConnectionConfiguration config = new ConnectionConfiguration(
  "localhost", 5222);

  /*
  * ConnectionConfiguration config = new ConnectionConfiguration(
  * "192.163.2.200", 5222);
  */
  XMPPConnection connection = new XMPPConnection(config);
  try {
  connection.connect();
  } catch (XMPPException e) {
 
  e.printStackTrace();
  }
  return connection;
  }



}

After execution of this you can see message in xmpp client spark as

How to remove Roster or Friend in xmpp server

In last post we have learn how to add roster in xmpp.  Now we will remove roster from roster list of any user. For  first you should  add roster in roster list of user. Now We get roster list of user and compare jabber id of roster and remove it using  removeEntry( RosterEntry ) method  . After remove roster you check roster using this article How to get roster of jabber id in xmpp server .

package com.javaproficiency.demo;

import java.util.Collection;

import org.jivesoftware.smack.ConnectionConfiguration;
import org.jivesoftware.smack.Roster;
import org.jivesoftware.smack.RosterEntry;
import org.jivesoftware.smack.XMPPConnection;
import org.jivesoftware.smack.XMPPException;



public class RemoveRoster {

  public static void main(String[] args) {

    AddRoster addRoster = new AddRoster();
 
XMPPConnection connection = addRoster.Connect();
try {
connection.login("yogesh@localhost","123");
System.out.println("Login");
Roster roster = connection.getRoster();
String removeJID = "shivam@localhost";
Collection<RosterEntry> entries = roster.getEntries();
for (RosterEntry entry : entries) {
          // remove roster whith removeJID
if (removeJID.equals(entry.getUser())) {
roster.removeEntry(entry);
}
}

           connection.disconnect();

} catch (XMPPException e) {

e.printStackTrace();
}
}


public XMPPConnection Connect() {
  
   ConnectionConfiguration config = new ConnectionConfiguration(
   "localhost", 5222);

   /*
    * ConnectionConfiguration config = new ConnectionConfiguration(
    * "192.163.2.200", 5222);
    */
   XMPPConnection connection = new XMPPConnection(config);
   try {
   connection.connect();
   } catch (XMPPException e) {
  
   e.printStackTrace();
   }
   return connection;
   }



}

how to add roster in xmpp using smack api

In last article we have learn how to login on xmpp server using smack api . Now In this article we will learn how to add friends( roster ) in buddy using smack api.For add roster in xmpp first you should make two account. See It how to resister on xmpp server if you do not know how to register user on xmpp server. after that you can send roster request using below code . 


package com.javaproficiency.demo;

import org.jivesoftware.smack.ConnectionConfiguration;
import org.jivesoftware.smack.Roster;
import org.jivesoftware.smack.Roster.SubscriptionMode;
import org.jivesoftware.smack.RosterEntry;
import org.jivesoftware.smack.XMPPConnection;
import org.jivesoftware.smack.XMPPException;
import org.jivesoftware.smack.packet.Presence;

public class AddRoster {

 public static void main(String[] args) {

   AddRoster addRoster = new AddRoster();
 
XMPPConnection connection = addRoster.Connect();
try {

                     // user yogesh login on xmpp server
connection.login("yogesh@localhost","123");
System.out.println("Login");

           Roster roster = connection.getRoster();
           // yogesh send roster request to shivam
           roster.createEntry("shivam@localhost","myking",null);

           System.out.println(" send roster request");
           connection.disconnect();

} catch (XMPPException e) {

e.printStackTrace();
}
}


public XMPPConnection Connect() {
 
  ConnectionConfiguration config = new ConnectionConfiguration(
  "localhost", 5222);

  /*
  * ConnectionConfiguration config = new ConnectionConfiguration(
  * "192.163.2.200", 5222);
  */
  XMPPConnection connection = new XMPPConnection(config);
  try {
  connection.connect();
  } catch (XMPPException e) {
 
  e.printStackTrace();
  }
  return connection;
  }


}

After execution  of this code you can see this output :

 Login

 

send roster request

And  

How to install Spark IM client in ubuntu

Spark Im client is xmpp client. You must read this article first  how to install openfire xmpp server in ubuntu. After that you need xmpp client for chating. Now We will learn how to Intall xmpp client in ubuntu.

Step 1: Download Xmpp Client Spark from this link http://www.igniterealtime.org/downloads/
 or you can download openfire from this website http://www.igniterealtime.org .

Step 2: Extract tar file.

Step 3: Go to Spark Folder and run this command

           ./Spark

Now you will see spark is running on you machine.

Step 4: Now you can login on xmpp server using spark

You can create new account on xmpp server using spark

Related Posts:

Connecting to XMPP IM with Smack for Java applications

Login to XMPP IM with Smack for Java applications

Get Roster List From XMPP IM with Smack API in Java Application

How To Install Openfire XMPP Server On Ubuntu

Step 1:

Downlaod Openfire from this link http://www.igniterealtime.org/downloads/
 or you can download openfire from this website http://www.igniterealtime.org

step 2:   Exact tar file

Step 3:  go to bin folder and run this command

          ./openfire start

On your terminal you get such message

openfire/bin$  ./openfire start
testing JVM in /usr ...
Starting openfire

step 4:  Now go to browser and hit url

   localhost:9090

if you use local machine otherwise use ip address of machine. We can see such page and click to continue .

Step 5:  In this step you will select domain and admin port. By default admin console port 9090 and secure admin port is 9091.Domain is ip address of machine. If you want to run openfire then you can use localhost as domain. Click continue for step step of openfire installation.

Step 6: In this step of openfire installation you will select database settings. If you donot know about it more i suggest to you click continue .

Step 7 :  In this  step you will select database for openfire. For example if i use mysql database then i fill all fields as requirement . i select mysql database then in database url i fill up database name and mysql hostname and more parameter as my requirements .  There is usename mysql usename and password is mysql password.

Step 8: Click to continue:

Step 9:  In This Step you will step administrator account of openfire. Select password for openfire admin.

Step 10. Click Login to admin console of openfire.

Step 11. Use usename and password for openfire administration , which are you have selected during openfire installation .

Step 12: See Openfire Admin Account as

After that you need to learn this tutorial for openfire devlopment  Openfire Tutorial



Related Posts:

Connecting to XMPP IM with Smack for Java applications

Login to XMPP IM with Smack for Java applications

Get Roster List From XMPP IM with Smack API in Java Application

Operators and datatypes In Java

Operator is a symbol that is used to perform operations on operands. There are many types of operators in java such as unary operator, arithmetic operator, relational operator, shift operator, bitwise operator, ternary operator and assignment operator.

Primitive Data Types

1. Integer
Integer types varaible can hold whole numbers such as 747 and −196. The size of the values that can be stored depends on the integer type that we choose.

Type Size Range of values that can be stored
byte 1 byte −128 to 127
short 2 bytes −32768 to 32767
int 4 bytes −2,147,483,648 to 2,147,483,647
long 8 bytes 9,223,372,036,854,775,808 to 9,223,372,036,854,755,807

The range of values is calculated as −(2n−1) to (2n−1)−1; where n is the number of bits required. For example, the byte data type requires 1 byte = 8 bits. Therefore, the range of values that can be stored in the byte data type is −(28−1) to (28−1)−1
= −27 to (27) -1
= −128 to 127

2. Floating Point
Floating point data types are used to represent numbers with a fractional part. Single precision floating point numbers occupy 4 bytes and Double precision floating point numbers occupy 8 bytes. There are two subtypes:

Type Size Range of values that can be stored
float 4 bytes 3.4e−038 to 3.4e+038
double 8 bytes 1.7e−308 to 1.7e+038
3. Character
It stores character constants in the memory. It assumes a size of 2 bytes, but basically it can hold only a single character because char stores unicode character sets. It has a minimum value of ‘u0000′ (or 0) and a maximum value of ‘uffff’ (or 65,535, inclusive).

4. Boolean
Boolean data types are used to store values with two states: true or false.

Related Post:

Top 50 core java coding interview question and answer 

Top 30 String programs

How to print numbers from 1 to 10 without using loop

Object cloning In Java

Given string is hexadecimal number or not

How Find out duplicate number between 1 to N numbers - Java Program

We have numbers from 1 to n  and one number is duplicate. Now we will find out duplicate number in given list. For this we will use formula sum of 1....n numbers.Firstly we will calculate the sum of list and sum of 1.... n number. Now difference between sum of list and sum of 1... n is equal to duplicate number .

sum of 1... n number = n*(n+1)/2


package com.javaproficiency;

import java.util.ArrayList;
import java.util.List;

public class FindDuplicateNumber {

public static void main(String[] args) {

ArrayList<Integer> list = new ArrayList<Integer>();
for (int i = 1; i < 10; i++) {
list.add(i);
}
list.add(5);
FindDuplicateNumber duplicateNumber = new FindDuplicateNumber();
System.out.println(" duplicate number ="+ duplicateNumber.getDuplicateNumber(list));
}

public  int getDuplicateNumber( ArrayList<Integer> list){

int size = list.size()-1;
int totalSum = (size*(size+1))/2;
int duplicateNumber = getSumOfList(list)- totalSum ;
return duplicateNumber;
}

public int getSumOfList( ArrayList<Integer> list){
int sum =0;
for (Integer num : list) {
sum += num;
}
return sum;
}


}

Output :

 duplicate number =5

Related Post:

Top 50 core java coding interview question and answer 

Top 30 String programs

How to print numbers from 1 to 10 without using loop

Object cloning In Java

Given string is hexadecimal number or not

How to convert Byte array to String in Java

In our application sometime there is need of byte array. We can use byte array for encryption purpose . We can convert a string to byte array using string getBytes() method. In byte array string become in decryted format . We can make string from byte array using this syntax.

String str = new String(ByteArray);

package com.javaproficiency;

public class StringToBinary {

public static void main(String[] args) {

String IPCode = "java string is good";

//convert string to byte  array

byte [] bytes = IPCode.getBytes();

System.out.println(" string ="+ IPCode);

System.out.println(" byte array ="+ bytes);

//Convert byte array to string 

String str = new String( bytes );

System.out.println(" str ="+  str);

}

}

Output:

 string =java string is good

 byte array =[B@6c267f18

 str =java string is good

Related Post:

Top 50 core java coding interview question and answer 

Top 30 String programs

How to print numbers from 1 to 10 without using loop

Object cloning In Java

Given string is hexadecimal number or not

How to check the given number is binary number or not -Java Program

In mathematics and digital electronics, a binary number is a number expressed in the binary numeral system or base-2 numeral system which represents numeric values using two different symbols: typically 0 (zero) and 1 (one). The base-2 system is a positional notation with a radix of 2. Below we have write a java program for check given number binary or not.

package com.javaproficiency;

public class IsBinary {

public static void main(String[] args) {

IsBinary isBinary = new IsBinary();

System.out.println(" num 101000 is binary = "+ isBinary.isBinary(101000) );
System.out.println(" num 101300 is binary = "+ isBinary.isBinary(101300) );
System.out.println(" num 101900 is binary = "+ isBinary.isBinary(101900) );
System.out.println(" num 10001 is binary = "+ isBinary.isBinary(10001) );


}


public boolean isBinary( int num ){

boolean flag = true;
while (num  > 0) {
int rem = num %10;
if (rem > 1) {
flag = false;
break;
}
num = num/10;
}
return flag;
}


}

Output:

 num 101000 is binary = true

 num 101300 is binary = false

 num 101900 is binary = false

 num 10001 is binary = true

How to convert binary to decimal number - Java Program

In this example we will convert binary to decimal using  java. We will use this logic

11 ==>>  1*2^1+1*2^0   == > 3

110 ==> 1*2^2+1*2^1+0*2^0  ==> 6

package com.javaproficiency;

public class BinaryToDecimal {

public static void main(String[] args) {

System.out.println(" decimal number ="+ getDecimalFromBinary(11));

}


public static int getDecimalFromBinary(int num ){
int decimal = 0 ;
int p = 0;
 while ( num > 0) {
 decimal += num %10 * Math.pow(2, p );
 num = num /10;
 p++;
}

return decimal;
}

}

Output:

decimal number = 3

Method Overriding Example - Java Program

package com.javaproficiency;


class Y {

void display(){
System.out.println(" Y is called");
}

}


public class X extends Y{

void display(){
System.out.println(" X is called");
}


public static void main(String[] args) {

    Y y = new Y();
    X x = new X();
    Y obj = new X();
   
    y.display();
    x.display();
    obj.display();
   
   

}

}

Output:

 Y is called

 X is called

 X is called

How to Find Common Element In Two arrays - java program

package com.javaproficiency;

public class CommonElementOfTwoArray {

public static void main(String[] args) {

  int []arr = {10,15,20,25,40};
       int []brr ={5,18,20,25,30,10};
     
       for( int i=0 ; i < arr.length ; i++ ){
            for( int j=0 ; j < brr.length ; j++  ){
                if(arr[i] == brr[j])
                    System.out.println(arr[i]);
            }
       }

}

}

Output:

10

20

25

Top 50 Core Java Coding / Programming Questions And Answers : Technical Interview In Java

If you want to be a developer when you can faced a technical round in your interview.Most of the student feel it hard round. But if you prepare in a right path, then you can clear your technical round easily.Most of student try to preparation  hardest technical interview question firstly. But some basic questions play a good roll in interviews. As my experience , I will share top core java  coding questions with answer. I hope , these question may be more helpful for all.

Program For nth Fibonacci Number in Java

How to find largest element in an array with index and value 

How to print array without using loop in java

Check number even or odd without using modulo operator

HCF and LCM of two number

Find duplicate charcters with occurrences in a string

Reverse string in java

Swap two number using bit operator

How to count the number of occurrences of a character in a string in java

How to print numbers from 1 to 10 without using loop?

How to Sort the String using string Method In java

Object Cloning in java example?

How to Make Singleton Class In Java

How to reverse a number in java

How to Check number is prime or not

How to count the number of occurrences of a character in a string in java

Count the number of occurrences of a character in a string is good programming questions . It is ask in colleges and schools mostly. This question also asked in many times in interviews. 

Method 1:

We can count number of occurrences of a character in a string with the help of indexOf() method.

package com.javaproficiency;

public class CountCharOccurance {

public static void main(String[] args) {

String str = "javaproficiencyexamplebyannu";

 

    String findStr = "a";

    int lastIndex = 0;

    int counter = 0;

 

    while (lastIndex != -1) {

 

     lastIndex = str.indexOf(findStr, lastIndex);

 

     if (lastIndex != -1) {

      counter++;

      lastIndex += findStr.length();

 

     }

    }

    System.out.println(counter);

}

}

Output: 

4

Method 2:

In this example we will use charAt() method of string for count number of occurrences of a character in a string .

package com.javaproficiency;

public class CountCharOccurancejava {

public static void main(String[] args) {

String s = "javaproficiencyexamplebyannu";

int counter = 0;

for( int i=0; i<s.length(); i++ ) {

   if( s.charAt(i) == 'a' ) {

       counter++;

   } 

}

System.out.println( counter );

}

}

Output:

4

How to print numbers from 1 to 10 without using loop?

We can print numbers 1 to 10 or 1 to 100 using recursion. Recursion is a good alternatives of loop. There we can use recursion to print numbers 1 to 10. We also use goto statement but in java we can not used goto statement. visit java keyword list http://docs.oracle.com/javase/tutorial/java/nutsandbolts/_keywords.html. So we will use here recursion.


package com.javaproficiency;

public class PrintNumber {

public static void main(String[] args) {

printNumberWithRecursion(1);

}

public static void printNumberWithRecursion(int n){

if (n <= 10) {
System.out.println(" number is ="+ n);
printNumberWithRecursion(n+1);
}

}

}

Output :

 number is =1

 number is =2

 number is =3

 number is =4

 number is =5

 number is =6

 number is =7

 number is =8

 number is =9

 number is =10

How to Sort the String using string Method In java

Java have a lot of method for string operations. We can sort a string by convert in to array of characters , now we will sort array after that we will make a new string from sorted array.Now our new string is in sorted order of characters.

package com.javaproficiency;

import java.util.Arrays;

public class StringSort {

public static void main(String[] args) {
String str = "xyabds";
char [] arr = str.toCharArray();
Arrays.sort(arr);
String sortedStr = new String(arr);
System.out.println(" sorted string = "+sortedStr);
}

}

Output:

 sorted string = abdsxy

Object Cloning in java example?

package com.javaproficiency;

public class Emp implements Cloneable {
//Object Cloning in java example?

int id;
String name;

public Emp(int id, String name) {
super();
this.id = id;
this.name = name;
}

public Emp clone() throws CloneNotSupportedException{

return (Emp ) super.clone();

}

public static void main(String[] args) {

Emp  emp = new Emp(10, "java");
Emp emp1 = null;
try {
emp1 = emp.clone();
} catch (CloneNotSupportedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

System.out.println(" clone object is ");
System.out.println("id ="+ emp1.id+ " name ="+ emp1.name);

}

}


Output:

 clone object is
 id =10 name =java

How to Make Singleton Class In Java

package com.javaproficiency;

public class SingletonDemo {

static SingletonDemo obj;
private  SingletonDemo(){
}

public static SingletonDemo getInstance(){
 if(obj!=null){
  return  obj;
 }
 else{
  obj=new SingletonDemo();
 return obj;
 }
}

public static void main(String[] args) {

SingletonDemo obj1 = SingletonDemo.getInstance();
SingletonDemo obj2 =  SingletonDemo.getInstance();

if( obj1 == obj2 ){
System.out.println(" singleton object ");
}else{
System.out.println(" not singleton object ");
}

System.out.println(obj1==obj2);
}


}

Output:

 singleton object
 true

How to reverse a number in java

package com.javaproficiency;

public class ReverseNumber {

public static void main(String[] args) {
int num =251;
int rNum =0;
while(num > 0){
rNum = rNum*10+ num%10;
num = num/10;
}
System.out.println(" reverse number is ="+rNum);
}
}


Output:

 reverse number is =152

How to Check number is prime or not

A number which is divided by one and itself is called prime number. For Example

7 is a prime number and
8 is not a prime number

package com.javaproficiency;

public class PrintPrime {

public static void main(String[] args) {
int i =101;
boolean flag = false;
for(int j=2 ; j <= i/2; j++){
if(i%j==0)
{
flag = true ;
break;
}
}
if(flag){
System.out.println(" number "+ i +" is not prime");
}else{
System.out.println(" number "+ i +" is  prime");
}

}

}


Output :

 number 101 is  prime

How to print array without using loop in java

How to print array without using loop in java is frequently asked question in interview. We can print array without using any loop. For this purpose we will use Arrays's method toString().

package com.javaproficiency;

import java.util.Arrays;

public class PrintArray {
//print array without using loop in java
public static void main(String[] args) {

int [] arr = {15,60,32,33,12};
System.out.println(" Print array ="+ Arrays.toString(arr));

char [] crr = {'A','B','C','D','E','F'};

System.out.println(" Print Array ="+ Arrays.toString(crr));

}

}


Output:

 Print array =[15, 60, 32, 33, 12]
 Print Array =[A, B, C, D, E, F]

How to find largest element in an array with index and value ?

package com.javaproficiency;

public class LargestElement {
//How to find largest element in an array with index and value ?

public static void main(String[] args) {

int [] arr ={4,5,10,12,8,6};
int largest =0;
int index =0;
for(int i =0 ; i < arr.length; i++){
if( largest < arr[i]){
largest = arr[i];
index = i;
}
}
System.out.println(" largest element  ="+ largest + " index ="+index);

}

}

Output :

 largest element  =12 index =3

Program For nth Fibonacci Number in Java

The Fibonacci numbers are the numbers in the following integer sequence.

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 141, ……..

In simple word such series that each element is sum of two previous element is called Fibonacci series.

In mathematical terms, the sequence Fn of Fibonacci numbers is defined by the recurrence relation

    Fn = Fn-1 + Fn-2

1. Program to print Fibonacci Series without using Recursion In Java

package com.javaproficiency;

public class Fibonacciseries {
public static void main(String[] args) {
//Fibonacci series without using Recursive?
int n=10;
int x = 1;
int y = 0;
int z =0;
System.out.print(y +" "+ x);
int i=0;
while(i < n){
z=y+x;
System.out.print("  "+ z);
y=x;
x=z;
i++;
}

}

}


output :

0 1  1  2  3  5  8  13  21  34  55  89

2. Program to print Fibonacci Series using Recursion In Java 

package com.javaproficiency;

public class Fibonacciserieswithrecursion {

    public static void main(String[] args) {
int n = 10;
int a =0 ;
int b =1;
System.out.print( a + " " + b);
fibonaci(n, a, b);
}
   
    static void fibonaci(int n , int a ,int b){
    int sum = 0;
    if (n > 0 ) {
    sum = a+b;
    a = b;
    b = sum;
System.out.print(" "+ sum);
    fibonaci(n-1, a, b);
}
   
   
    }

}


output:

0 1 1 2 3 5 8 13 21 34 55 89

Activator Eclipse Command is not working In PlayFramwork

When i run 

activator eclipse

command then i get following error.

[info] Set current project to demo (in build file:/home/anuj/playapp/demo/)
[error] Not a valid command: eclipse (similar: help, alias)
[error] Not a valid project ID: eclipse
[error] Expected ':' (if selecting a configuration)
[error] Not a valid key: eclipse (similar: deliver, licenses, clean)
[error] eclipse
[error]        ^

How can i import scala project to eclipse ?

I run this command for scala project import to eclipse . But when i run activator eclipse command , i get error.

Solution:

Go to project folder inside your project and Append this below to your plugins.sbt file:

addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "4.0.0")

now run again

activator eclipse command and you will run this command now successfully. After that you can import this project to eclipse.

java.lang.UnsupportedClassVersionError: com/typesafe/config/ConfigException : Unsupported major.minor version 52.0

java.lang.UnsupportedClassVersionError: com/typesafe/config/ConfigException : Unsupported major.minor version 52.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
    at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
    at com.typesafe.sbt.web.SbtWeb$$anonfun$com$typesafe$sbt$web$SbtWeb$$load$1.apply(SbtWeb.scala:535)
    at com.typesafe.sbt.web.SbtWeb$$anonfun$com$typesafe$sbt$web$SbtWeb$$load$1.apply(SbtWeb.scala:535)
    at scala.Option.fold(Option.scala:157)
    at com.typesafe.sbt.web.SbtWeb$.com$typesafe$sbt$web$SbtWeb$$load(SbtWeb.scala:549)
    at com.typesafe.sbt.web.SbtWeb$$anonfun$globalSettings$1$$anonfun$apply$1.apply(SbtWeb.scala:143)
    at com.typesafe.sbt.web.SbtWeb$$anonfun$globalSettings$1$$anonfun$apply$1.apply(SbtWeb.scala:143)
    at scala.Function1$$anonfun$andThen$1.apply(Function1.scala:55)
    at sbt.Project$.setProject(Project.scala:319)
    at sbt.BuiltinCommands$.doLoadProject(Main.scala:484)
    at sbt.BuiltinCommands$$anonfun$loadProjectImpl$2.apply(Main.scala:475)
    at sbt.BuiltinCommands$$anonfun$loadProjectImpl$2.apply(Main.scala:475)
    at sbt.Command$$anonfun$applyEffect$1$$anonfun$apply$2.apply(Command.scala:58)
    at sbt.Command$$anonfun$applyEffect$1$$anonfun$apply$2.apply(Command.scala:58)
    at sbt.Command$$anonfun$applyEffect$2$$anonfun$apply$3.apply(Command.scala:60)
    at sbt.Command$$anonfun$applyEffect$2$$anonfun$apply$3.apply(Command.scala:60)
    at sbt.Command$.process(Command.scala:92)
    at sbt.MainLoop$$anonfun$1$$anonfun$apply$1.apply(MainLoop.scala:98)
    at sbt.MainLoop$$anonfun$1$$anonfun$apply$1.apply(MainLoop.scala:98)
    at sbt.State$$anon$1.process(State.scala:184)
    at sbt.MainLoop$$anonfun$1.apply(MainLoop.scala:98)
    at sbt.MainLoop$$anonfun$1.apply(MainLoop.scala:98)
    at sbt.ErrorHandling$.wideConvert(ErrorHandling.scala:17)
    at sbt.MainLoop$.next(MainLoop.scala:98)
    at sbt.MainLoop$.run(MainLoop.scala:91)
    at sbt.MainLoop$$anonfun$runWithNewLog$1.apply(MainLoop.scala:70)
    at sbt.MainLoop$$anonfun$runWithNewLog$1.apply(MainLoop.scala:65)
    at sbt.Using.apply(Using.scala:24)
    at sbt.MainLoop$.runWithNewLog(MainLoop.scala:65)
    at sbt.MainLoop$.runAndClearLast(MainLoop.scala:48)
    at sbt.MainLoop$.runLoggedLoop(MainLoop.scala:32)
    at sbt.MainLoop$.runLogged(MainLoop.scala:24)
    at sbt.StandardMain$.runManaged(Main.scala:53)
    at sbt.xMain.run(Main.scala:28)
    at xsbt.boot.Launch$$anonfun$run$1.apply(Launch.scala:109)
    at xsbt.boot.Launch$.withContextLoader(Launch.scala:128)
    at xsbt.boot.Launch$.run(Launch.scala:109)
    at xsbt.boot.Launch$$anonfun$apply$1.apply(Launch.scala:35)
    at xsbt.boot.Launch$.launch(Launch.scala:117)
    at xsbt.boot.Launch$.apply(Launch.scala:18)
    at xsbt.boot.Boot$.runImpl(Boot.scala:41)
    at xsbt.boot.Boot$.main(Boot.scala:17)
    at xsbt.boot.Boot.main(Boot.scala)
[error] java.lang.UnsupportedClassVersionError: com/typesafe/config/ConfigException : Unsupported major.minor version 52.0
[error] Use 'last' for the full log.

solution:

Still you are using java7. You can download java8. If you already install java8 make sure it is active.You can change java version using bellow commands.

How To Change Java Version 

 

$ sudo update-alternatives --config java

There are 2 choices for the alternative java (providing /usr/bin/java).

  Selection    Path                                            Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java   1061      auto mode
  1            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java   1061      manual mode
  2            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1051      manual mode

Press enter to keep the current choice[*], or type selection number: 2

update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java
to provide /usr/bin/java (java) in manual mode

 

 Now you can check you java version using below command

java -version