Skip to main content

Java- Interview


Here are some popular tips in Java

General Question

  • JVM - Java Virtual Machine. Used to execute byte code. Platform dependent (but byte code is platform independent)
  • JRE- Java Run time Environment. It provides run time environment and it's the implementation of JVM. It contains libraries and files that need to execute JVM.  
  • JDK- Java Development Kit. It contains JRE and development tools.
  • Why java doesn't support pointers: It's insecure and complex to understand
  • We can save java file with another name if class is not defined as public
  • Java use camalCase notation for objects naming (ex: firstName)

OOP Concepts Related 

  • Aggregation: weak relationship (bike has an indicator)
  • Composition:  strong relationship (bike has an engine)

GUI

  • Java GUI - Install Window builder to create GUI using Eclipse IDE

Code Related

  • No issues when you write static public void instead of public static void
  • We can execute program without main method : using static block 
  • this : refer the current object
  • Super class of every class : object class
  • Can't use both super() and this() in constructor at once
  • Can overload main method
  • Can declare main method as final
  • final class
    • can't inherit

Variables Related 

  • Local variables are not initialized to any default value
  • Static variables: 
    • used to refer the common property of all objects
  • final variables:
    • can't change the value

Method Related 

  • Constructor: It is a method that used to create objects
  • Return value of constructor : current instance
  • Constructor can't inherit and can't define as final
  • Static methods :
    • can invoke without initializing objects
    • can't override (Because they are part of the class, not the object)
  • final methods:
    • can't override
  • main method is static: because it's invoked before  initializing objects
  • If static keyword is removed from main method: program compiles but gives run time error




Comments

Post a Comment

Popular posts from this blog

Sorting Algorithms

Bubble Sort Named as sinking sort. Compare each pair of the adjacent items and swap them if they are in the wrong order. Worst case and average case time complexity both O(n^2)  and best case time complexity is O(n).
Post a Comment
Read more

JavaScript Objects and Prototypes

Create Objects Using function Create Objects without duplication code: use functions Using constructors To indicate a function is a constructor:  append new keyword in front of the function name when executing it Call Property of function object foo.call() = foo() Call can bind different objects and can execute functions __proto__ Copy of prototype object If some property is not in the object itself, it then looks it in the prototype. If it finds it returns the value of that property All the new object instances of function point to same prototype object prototype.constructor: property that points to function  GitHub repo:  https://github.com/kaosadi17/JavaScript/blob/master/objects%26prototypes.js
Post a Comment
Read more

Introduction to JQuery

JQuery Open source JavaScript library. Cross browser compatibility Include the JQuery code inside this function       $(document).ready(function(){             your code is here             }); Creating CSS element : nothing added (body{}) class name : added fullstop (.clzname{}) id : added slash (#idname{}) JQuery Methods  click(): can include actions when after clicking defined button $("button").click mouseover: can include actions when over the mouse on defined element $(button').mouseover hover : can include tow functions when the mouse is over it and not $("img").hover load : execute when complete page is fully loaded  $("img").load JQuery Actions hide() : hide the defined content $("#right").hide() html() : change the html element with defined content $("p").html("<p>My content<p>") text() :  change the content as defined text $("p")
Post a Comment
Read more