IT Knowledge Sharing | Interview questions

See the code: class GFC304 { static void m1(int[] i1, int[] i2) { int[] i3 = i1; i1 = i2; i2 = i3; } public static void main (String[] args) { int[] i1 = {1}, i2 = {3}; m1(i1, i2); System.out.print(i1[0] + "," + i2[0]); }} What will be the output? Answer: 1,3 Explanation: Here we are passing the copy of reference variables  i1 and i2 from main() method to method m1(). Now m1 has it's own  local reference variables i1 and i2 referring to same array as main() method's i1 and i2. So you can see that we are only passing the  reference variables not exactly the value they are refering. See this figure... Now see the second code....... class GFC305 { static void m1(int[] i1, int[] i2) { int i = i1[0]; i1[0] = i2[0]; i2[0] = i; } public static void main (String[] args) { int[] i1 = {1}, i2 = {3}; m1(i1, i2); System.out.print(i1[0] + "," + i2[0]); }} What will be the output? Answer: 3,1 Exp...

The code is given: 3.  public class Bertha { 4.    static String s = ""; 5.    public static void main(String[] args) { 6.        int x = 4; Boolean y = true; short[] sa = {1,2,3}; 7.        doStuff(x, y); 8.        doStuff(x); 9.        doStuff(sa, sa); 10.       System.out.println(s); 11.   } 12.   static void doStuff(Object o) { s += "1"; } 13.   static void doStuff(Object... o) { s += "2"; } 14.   static void doStuff(Integer... i) { s += "3"; } 15.   static void doStuff(Long L) { s += "4"; } 16. } What is the result? A. 212 B. 232 C. 234 D. 312 E. 332 F. 334 G. Compilation fails Answer:  A is correct.  Explanation: It's legal to autobox and then widen. The first call to doStuff(), x is boxed from int to an Integer then passes these two objects (Integer,Boolean) to varargs (Object.... 0). The second...

Overloading with Boxing and Var-args class AddBoxing {   static void go(Integer x) { System.out.println("Integer"); }     public static void main(String [] args) {      int i = 5;      go(i);    } } Answer: Integer class AddBoxing {    static void go(long x) { System.out.println("long"); }   public static void main(String [] args) {      int i = 5;      go(i);    } } Answer: long Now see... class AddBoxing {   static void go(Integer x) { System.out.println("Integer"); }   static void go(long x) { System.out.println("long"); }   public static void main(String [] args) {      int i = 5;      go(i); // which go() will be invoked?   } } If it is given that both methods exist, which one will be used? In other words, does the compiler think that widening a primitive parameter is more desirable than...

Qu1. See the code ... 3.   class Dozens { 4.      int[] dz = {1,2,3,4,5,6,7,8,9,10,11,12}; 5.   } 6.   public class Eggs { 7.         public static void main(String[] args) { 8.               Dozens [] da = new Dozens[3]; 9.               da[0] = new Dozens(); 10.             Dozens d = new Dozens(); 11.             da[1] = d; 12.             d = null; 13.             da[1] = null; 14.            // more code 15.       } 16.  } Which two are true about the objects created within main(), and eligible for garbage collection when line 14 is reached? A. Three objects were created B. Four objects were created C. Five objects were created D. Zero objects are ...

Qu1: Can you write a small generic class by yourself ? Answer: This could be like this...... public class GenericClassDemo<X, Y> {    X name;    Y age;    GenericClassDemo(X name, Y age) {       this.name = name;       this.age = age;    }    X getX() { return name; }    Y getY() { return age; }    // test it by creating it with <String, Integer>   public static void main (String[] args) {        GenericClassDemo<String, Integer> obj=                       new GenericClassDemo<String, Integer>("Rajesh Kumar", 15);        String empName = obj.getX();    // returns a String        int empAge = obj.getY();    // returns Integer, unboxes to int        System.out.print...

Ploymorphism with Generics Generic collections give us sane advantages of type safety that we have always had with arrays, but there are some crucial differences Most of these have to do with polymorphism. You've already seen that polymorphism applies to the "base" type of the collection: List<Integer> myList = new ArrayList<Integer>(); In other words, we were able to assign an ArrayList to a List reference, because List is a supertype of ArrayList. But what about this? class Parent { } class Child extends Parent { } List<Parent> myList = new ArrayList<Child>(); No, it will not work. Rule : The type of the variable declaration must match the type you pass to the actual object type. If you declare List<Parent> parentList then whatever you assign to the foo reference MUST be of the generic type <Parent>. Not a subtype of <Parent>. Not a supertype of <Parent>. Just <Parent>. Wrong: List<Obj...

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Understand hashCode() and equals() in HashMap Always remember that when you are using a class that implements Map or any classes that you are using as a part of the keys for that map must override the hashCode() and equals() methods. Let's see the following example.... ----------------------------------- import java.util.*; class MapEQ2 {   public static void main(String[] args) {        Map<ToDos, String> m = new HashMap<ToDos, String>();                ToDos t1 = new ToDos("Monday");        ToDos t2 = new ToDos("Monday");        ToDos t3 = new ToDos("Tuesday");        System.out.println("Putting first object::");        m.put(t1, "doLaundry");        System.out.println("\n Putting second object::");        m.put(t2, "payBills");        System.out...

When we insert a big data into a cell then it inserts a page break and goes to next page automatically.... To solve this we can use   setSplitLate(false) method on table to be created in itext pdf doc. See the complete code here...... package com.example; import com.itextpdf.text.Document; import com.itextpdf.text.Element; import com.itextpdf.text.Paragraph; import com.itextpdf.text.pdf.PdfPCell; import com.itextpdf.text.pdf.PdfPTable; import com.itextpdf.text.pdf.PdfWriter; import java.io.FileOutputStream; public class PdfTableExample {   public static void main(String[] args) {  System.out.println("Going to create pdf...");     Document document = new Document();     try {       PdfWriter.getInstance(document,      new FileOutputStream("C://Test.pdf"));       document.open();       PdfPTable table = new PdfPTable(1); //1 column.      ...

Nested table in iText to cerate pdf using Java Suppose you are using iText to create pdf document using java, then this program will help you to create a table inside a table. ------------------------------------------------------------------ import com.itextpdf.text.Document; import com.itextpdf.text.Paragraph; import com.itextpdf.text.pdf.PdfPCell; import com.itextpdf.text.pdf.PdfPTable; import com.itextpdf.text.pdf.PdfWriter; import java.io.FileOutputStream; public class NestedTableExample {   public static void main(String[] args) {     Document document = new Document();     try {       PdfWriter.getInstance(document,      new FileOutputStream("NestedTableDemo.pdf"));       document.open();       PdfPTable table = new PdfPTable(2); // 2 columns.       PdfPCell outerTableCell1 = new PdfPCell(new Paragraph("Outer Table :Cell 1"));       PdfP...

Please see the folowing URL: http://maps.googleapis.com/maps/api/staticmap?size=512x512&maptype=roadmap\& markers=size:mid|color:blue| icon:http://knowledgeserve.in/images/logo.png |San+Francisco,CA|Oakland,CA|San+Jose,CA&sensor=false See icon: http://knowledgeserve.in/images/logo.png , here you can give the image path, wherever it is.. So change your image link and then copy and paste this URL.

Interceptor continue..... If you want to use an interceptor which will check whether the session has been expired or not, if it is expired then it will forward to global view( like any jsp that you want to display after session timeout). You need to do the following coding... 1) Make an interceptor file  SessionCheckInterceptor .java ---------------------------------------------------- package com.example.web.interceptor; import java.util.Map; import com.opensymphony.xwork2.ActionContext; import com.opensymphony.xwork2.ActionInvocation; import com.opensymphony.xwork2.interceptor.Interceptor; import com.vicwalks.web.util.LogManager; import com.vicwalks.web.util.VicWalkConstants; public class SessionCheckInterceptor implements Interceptor { private static final long serialVersionUID = 1L; public void destroy() { LogManager.info(this," SessionCheckInterceptor destroy() is called..."); } public void init() { LogManager.info(this," ...