The createNewFile() method of the File class is used to create a new empty file if a file with the given name does not already exist. It returns true if a file with the given name does not exist and is successfully created; otherwise, it returns false.

class TestInstanceof {
public static void main(String[] args) {
Integer i=5;
Boolean b;
b=(i instanceof Integer);
System.out.print(b);
b=(i instanceof Number);
System.out.println(b);
}
}

A: Adding objects to a collection
B: Iterating through a collection
C: Finding out if an object is in a collection
D: Retrieving an object from a collection

All answer options are correct because:

The Collections Framework in Java is a hierarchy of interfaces and classes that provides a technology for managing a group of objects. It is used to provide a central and unified theme for managing a group of objects. The Java Collections Framework is designed to meet the following goals:

• To offer high performance in terms of efficiency.
• To allow different types of collections to work in a similar way and with a high degree of interoperability.
• To ensure collections are flexible and can be easily extended.

Following are the basic types of operations allowed in a collection:

• Adding objects to a collection
• Removing objects from a collection.
• Retrieving an object from a collection.
• Finding out if an object is in a collection.
• Iterating through a collection.

import java.util.*;
public class TestArray{
public static void main(String[] args){
TestArray test = new TestArray();
test.go();
}
public void go(){
int[] arr = new int[] {1,2,3,4,5,6};
//add code here
}
}

public class Exc
{
public static void main(String args[])
{
int x1=0;
try {
int x3= 100/x1;
} catch(ArithmeticException e) {
System.out.println(“Illegal operation”);
} catch(RuntimeException e) {
System.out.println(“runtime error”);
return;
} catch(Exception e) {
System.out.println(“Exception found”);
} finally {
System.out.println(“Complete”);
}
System.out.println(“Successfully”);
}
}

class Ques0357{
public static void main(String[] argv){
int s = 2;
switch (s) {
case 1:
System.out.println(“Fred”);
break;
case 2:
System.out.println(“Fast”);
case 3:
System.out.println(“Tech”);
default:
System.out.println(“default”);
}
}
}

The break statement is used inside the code block following the switch statement to terminate the execution of a statement sequence. As soon as a break statement is encountered, the program control is transferred to the first line of code that follows the entire switch statement.

In the given program, the argument to the switch statement is an int value 2. Therefore, the program control will be transferred at the matching case label, i.e., at line number 8. As there is no break statement after line number 7, the execution of the code will continue to fall through and all the statements after line number 8 will be executed. Therefore, the execution of the program will display Fast Tech default as the output.

http://www.scjp-certification.com/what-is-the-for-each-loop.html

If a class Student creates two student objects. Which of the following statements are true about its constructors?

A: The compiler can call to super() in any constructor that has a call to this().
B: If a constructor is not declared in the code, a default constructor will be automatically generated by the compiler.
C: Constructors can be overridden.
D: The compiler cannot call to super() in any constructor that has a call to this()

ANSWERS:

If a constructor has a call to this(), the compiler will know that the constructor is not using the call to super(). A constructor can never have both a call to super() and a call to this() because one of these will be used as the first statement in the constructor. The compiler will not put a call to super() that is using a call to this().

If a constructor is not declared in the code, a default constructor will be automatically generated by the compiler. A constructor without any parameters is known as a default constructor. When a class is defined without any constructor, the Java compiler provides an implicit default constructor.

When the implicit default constructor of a class is invoked, it implicitly calls the no parameter constructor in the superclass. This action taken by a default constructor ensures that the inherited state of the object is initialized properly. In addition, it initializes all the instance variables in the object to the default value depending on their data type.

The default constructor of a class has the same access modifier with which the class has been declared. For example, the default constructor of a public class is implicitly given the public access. The default constructor of a protected class is implicitly given the protected access. The default constructor of a private class is implicitly given the private access. Otherwise, the default constructor has the default access implied by no access modifier.

import java.util.EnumSet;
public final class EnumMeg
{
public static void main(String[] args)
{
Integer i = null;
method(i);
}
static void method(int k){
System.out.println(k);
}
}

It will compile but will throw a NullPointerException at runtime.

class Ques{
public static void main (String[] argv){
int p1 = 0102;
int p2 = -10;
int mod = p1 % p2;
System.out.println(“mod = ” +mod);
}
}