Following books are on top from popularity and content wise and are a good resource to learn java programming from beginner to advance level.

All Java components require names. Names used for classes, variables and methods are called identifiers. In Java, there are several points to remember about identifiers. They are as follows -All identifiers should begin with a letter (A to Z or a to z), currency character ($) or an underscore (_). After the first character, identifiers can have any combination of characters.A keyword cannot be used as an identifier. Most importantly, identifiers are case sensitive. Examples of legal identifiers: age, $salary, _value, __1_value. Examples of illegal identifiers: 123abc, -salary.

Following books are on top from popularity and content wise and are a good resource to learn java programming from beginner to advance level.

There are many sites which are a good resource for java interview questions-answers. Following is the list of most popular websites.Tutorialspoint - www.tutorialspoint.comStackOverflow - www.stackoverflow.comDZone - www.dzone.comWikipedia - www.wikipedia.orgIBM Developer Works - www.ibm.com/developerworks/java/TechGig - www.techgig.comGitHub - www.github.comJava documentation - docs.oracle.com/javase/Coursera - www.coursera.org/JavaWorld - www.javaworld.com/

There are many sites which are a good resource to learn java. Following is the list of most popular websites.Tutorialspoint - www.tutorialspoint.comStackOverflow - www.stackoverflow.comDZone - www.dzone.comWikipedia - www.wikipedia.orgIBM Developer Works - www.ibm.com/developerworks/java/TechGig - www.techgig.comGitHub - www.github.comJava documentation - docs.oracle.com/javase/Coursera - www.coursera.org/JavaWorld - www.javaworld.com/

There are many sites which are good resource for java interview questions-answers. Following is the list of most popular websites.Tutorialspoint www.tutorialspoint.comStackOverflow www.stackoverflow.comDZone www.dzone.comWikipedia www.wikipedia.orgIBM Developer Works www.ibm.com/developerworks/java/TechGig www.techgig.comGitHub www.github.comJava documentation docs.oracle.com/javase/Coursera www.coursera.org/JavaWorld www.javaworld.com/

There are many sites which are a good resource for java interview questions-answers. Following is the list of most popular websites.Tutorialspoint  - www.tutorialspoint.comStackOverflow - www.stackoverflow.comDZone - www.dzone.comWikipedia - www.wikipedia.orgIBM Developer Works - www.ibm.com/developerworks/java/TechGig - www.techgig.comGitHub - www.github.comJava documentation - docs.oracle.com/javase/Coursera - www.coursera.org/JavaWorld - www.javaworld.com/

There are many sites which are a good resource for java interview questions-answers. Following is the list of most popular websites.Tutorialspoint - www.tutorialspoint.comStackOverflow - www.stackoverflow.comDZone - www.dzone.comWikipedia - www.wikipedia.orgIBM Developer Works - www.ibm.com/developerworks/java/TechGig - www.techgig.comGitHub - www.github.comJava documentation - docs.oracle.com/javase/Coursera - www.coursera.org/JavaWorld - www.javaworld.com/

From Java 8 onwards, the lambda expression is introduced which acts as function pointers.Lambda expressions are introduced in Java 8 and are touted to be the biggest feature of Java 8. Lambda expression facilitates functional programming and simplifies the development a lot.SyntaxA lambda expression is characterized by the following syntax.parameter -> expression bodyFollowing are the important characteristics of a lambda expression.Optional type declaration − No need to declare the type of a parameter. The compiler can inference the same from the value of the parameter.Optional parenthesis around parameter − No need to declare a single parameter in parenthesis. For multiple ... Read More

You should get a start time before making a call and end time after method execution. The difference is the time taken. ExampleLive Demoimport java.util.Calendar; public class Tester {    public static void main(String[] args) {       long startTime = Calendar.getInstance().getTimeInMillis();       longRunningMethod();       long endTime = Calendar.getInstance().getTimeInMillis();       System.out.println("Time taken: " + (endTime - startTime) + " ms");    }    public static void longRunningMethod() {       try {          Thread.sleep(1000);       } catch (InterruptedException e) {          e.printStackTrace();       }    } }OutputTime taken: 1012 ms