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Q3061. Write an SQL to find all records having all numeric characters in a field ?

Ans. Select * from Table where isnumeric(field) = 1;

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Q3062. When does an application throw NullPointerException ?

Core Java

Ans. When it tries to access an object element or method using reference which is actually null.

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Q3063. How can we protect an application from throwing a NullPointerException ?

Ans. By having Null Checks.

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Q3064. What are the conventions regarding constant variables or static final variables ?

Core Java

Ans. They should be named all in upper case with underscore separating words.

Moreover the name should be such that it identifies the value. For example, if we are using constant for employee Id 123, it should be named something like EMPLOYEE_ID_123 and not EMPLOYEE_ID

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Q3065. How do you define a class of constants in Java?

Ans. Make the class as final.
Disable the object construction by making constructor private.
Keep only Static Final Variables declared and Defined at the same time.

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Q3066. What are the steps to be performed while coding Junit with Mocking framework ?

JUnit

Ans. Initialize required objects for working with mocks and tested method
Set the mock behaviour on dependent objects
Execute the tested method
Perform assertions
Verify if a method is invoked or not

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Q3067. Name few Dependency Injection frameworks ?

Ans. Google Guice , Spring , PicoContainer and Dagger.

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Q3068. If you are given a choice to implement the code to either Insert a Record or Update if already exist, Which approach will you follow ?

1. Insert into the DB Table. If exception occurs, update the existing record.
2. Check if the record exists and update it if it exists, If not insert a new record.

Solution

Ans. In first case, there would be 2 DB calls in worst case and 1 in best case. In 2nd approach there will be always 2 DB calls.

Decision on the approach should depend on the following considerations -

1. How costly is the call to DB ? Are we using indices , hibernate etc

If calls to DB are costly , 1st approach should be the choice.

2. Exception Book keeping load upon exception.

The benefit of saving 1st call in approach 1 should be bigger than the Book keeping for the exception.

3. Probability of the exception in first apparoach.

If the DB Table is almost empty, it makes sense to follow Approach 1 as majority of the 1st calls will pass through without exception.

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Q3069. What will the following code do ?

String dateStr = "2011 11 19";
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
Date date = dateFormat.parse(dateStr);
System.out.println(date);

Ans. It will throw the ParseException as the date format doesn't abide with the format of the specified date.

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Q3070. What will be the output of this code ?

Set mySet = new HashSet();
mySet.add("4567");
mySet.add("5678");
mySet.add("6789");
for(String s: mySet){
System.out.println(s);
}

Ans. It will print 4567,5678 and 6789 but Order cannot be predicted.

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Q3071. What will be the output of this code ?

Set mySet = new TreeSet();
mySet.add("4567");
mySet.add("5678");
mySet.add("6789");
for(String s: mySet){
System.out.println(s);
}

Ans. 4567
5678
6789

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Q3072. What will be the output of this code ?

Set mySet = new HashSet();
mySet.add("4567");
mySet.add("5678");
mySet.add("6789");
System.out.println(s.get(0));

Ans. This will give compile time error as we cannot retrieve the element from a specified index using Set. Set doesn't maintain elements in any order.

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Q3073. public enum Day {
SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
THURSDAY, FRIDAY, SATURDAY
}

public class Test {
Set mySet = new HashSet();
mySet.add(Day.MONDAY);
mySet.add(Day.SUNDAY);
mySet.add(Day.SATURDAY);

for(Day d: mySet){
System.out.println(d);
}
}

Ans. SUNDAY
MONDAY
SATURDAY

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Q3074. What will be the output of the following code ?

enum Day {
   MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY,SUNDAY
}

public class BuggyBread1{
   public static void main (String args[]) {
      Set mySet = new HashSet();
      mySet.add(Day.SATURDAY);
      mySet.add(Day.WEDNESDAY);
      mySet.add(Day.FRIDAY);
      mySet.add(Day.WEDNESDAY);
      for(Day d: mySet){
         System.out.println(d);
      }
   }
}

Ans. FRIDAY , SATURDAY and WEDNESDAY will be printed but the order cannot be determined.

Only one FRIDAY will be printed as Set doesn't allow duplicates. Order cannot be determined as HashSet doesn't maintain elements in a particular order.

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Q3075. What will be the output of the following code ?

enum Day {
MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY,SUNDAY
}

public class BuggyBread1{
public static void main (String args[]) {
Set mySet = new TreeSet();
mySet.add(Day.SATURDAY);
mySet.add(Day.WEDNESDAY);
mySet.add(Day.FRIDAY);
mySet.add(Day.WEDNESDAY);
for(Day d: mySet){
System.out.println(d);
}
}
}

Core Java

Ans. WEDNESDAY
FRIDAY
SATURDAY

Only one FRIDAY will be printed as Set doesn't allow duplicates.Elements will be printed in the order in which constants are declared in the Enum. TreeSet maintains the elements in the ascending order which is identified by the defined compareTo method. compareTo method in Enum has been defined such that the constant declared later are greater than the constants declared prior.

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Q3076. public class BuggyBread1{

public static void main (String args[]) {
Set<String> mySet = new TreeSet<String>();
mySet.add(""1"");
mySet.add(""2"");
mySet.add(""111"");
for(String d: mySet){
System.out.println(d);
}
}
}

Core Java

Ans. 1
111
2

TreeSet maintains the elements in the ascending order which is identified by the compareTo method. compareTo method in String has been defined such that it results in the natural alphabetic Order. Here the elements in the TreeSet are of String and not of Integer. In String Natural Order, 111 comes before 2 as ascii of 1st character first determines the order.

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Q3077. public class BuggyBread1{

public static void main (String args[]) {
Set<Integer> mySet = new TreeSet<Integer>();
mySet.add(1);
mySet.add(2);
mySet.add(111);
for(Integer d: mySet){
System.out.println(d);
}
}
}

Core Java

Ans. 1
2
111

TreeSet maintains the elements in the ascending order which is identified by the compareTo method. compareTo method in Integer has been defined such that it results in the natural numerical Order.

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Q3078. Can we extend an Enum ?

Core Java

Ans. No. Enums are final by design.

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Q3079. What would you do if you have to add a jar to the project using Maven ?

Maven

Ans. If its already there in Maven local repository, We can add that as a dependency in the project pom file with its Group Id, Artifact Id and version.

We can provide additional attribute SystemPath if its unable to locate the jar in the local repository.

If its not there in the local repository, we can install it first in the local repository and then can add it as dependency.

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Q3080. Have you ever had problem getting your projects in eclipse refreshed after you made changes in the Pom files ?

Maven

Ans. Yes, It happens many times but I would usually perform mvn eclipse:eclipse and this would resolve the project refresh problems.

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Q3081. What is the difference between compile and install ?

Maven

Ans. Compile compiles the source code of the project

whereas

Install installs the package into the local repository, for use as a dependency in other projects locally

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Q3082. How can we change the JDK compliance level ?

Eclipse

Ans. Windows -> Preferences -> Java - Compiler -> Java Compliance Level

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Q3083. Can I use different Java versions for building different Eclipse projects ?

Eclipse

Ans. Yes. We can assign different JRE System libraries by going to

Java Build Path -> Libraries

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Q3084. How to perform a clean install without executing Tests ?

Maven

Ans. mvn clean install -Dmaven.test.skip=true

or

mvn install -DskipTests

or

org.apache.maven.plugins
maven-surefire-plugin

true

within parent POM file.

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Q3085. How to generate getters and setters automatically in eclipse ?

Eclipse

Ans. Right Click -> Source -> Generate Getters and Setters.

and it will open up a dialog wherein we can select the fields to generate Getters and Setters.

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Q3086. What are the considerations to be made in case of loops in Java ?

Core Java

Ans. 1. It shouldn't result in infinite loop. Please make sure that you have a condition that will terminate the loop and that condition should be reached.

2. Make sure to use the break statement if you aspire to only look for something. Not using break will unnecessarily execute it till the end of for loop in some cases.

3. Similarly use continue to execute the loop with next iteration and bypass the rest of the code block if required.

4. Try to avoid multiple nesting of for loops. If it''s required, Make sure to use break and continue properly so as to avoid some unnecessary processing.

5. Make sure to use try catch within the loop and not outside the for loop if you expect it to continue if one of the iteration fails.

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Q3087. Shouldn't we make a class with all static members is its just expected to be executed as a standalone program with just one thread. Moreover Lets assume that there is no runtime Polymorphism required and there is no need for serialization ?

Design

Ans. Still No in case we are making use of inheritance. we may have problem wherein we have program flow moving across common inherited method and specific methods of the derived class. call made to another static method in the parent class will only access the static class of the Parent class irrespective of the call from any of the derived class.

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Q3088. Tell me something about AssertionError ?

Core Java

Ans. AssertionError is actually a fatal fault or a bug in the program. We may not like to continue program , request or thread execution if this error occurs as this condition is the assumption to continue further execution.

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Q3089. Should we create system software ( e.g Operating system ) in Java ?

Core Java

Ans. No, Java runs on a virtual machine called JVM and hence doesn't embed well with the underlying hardware. Though we can create a platform independent system software but that would be really slow and that's what we would never need.

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Q3090. What is Java primarily used for ?

Core Java

Ans. For creating platform independent software applications.

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