Technical Interview Question and Answers Java 2016.
Technical Interview Question and Answers
Interview Questions on Java
What if the main method is declared as private?
The program compiles properly but at runtime it will give “Main method not
public.” message.
What is meant by pass by reference and pass by value in Java?
Pass by reference means, passing the address itself rather than passing the value.
Pass by value means passing a copy of the value.
If you’re overriding the method equals() of an object, which other method you
might also consider?
hashCode()
What is Byte Code?
Or
What gives java it’s “write once and run anywhere” nature?
All Java programs are compiled into class files that contain bytecodes. These byte
codes can be run in any platform and hence java is said to be platform
independent.
Expain the reason for each keyword of public static void main(String args[])?
public- main(..) is the first method called by java environment when a program is
executed so it has to accessible from java environment. Hence the access specifier
has to be public.
static: Java environment should be able to call this method without creating an
instance of the class , so this method must be declared as static.
void: main does not return anything so the return type must be void
The argument String indicates the argument type which is given at the command line
and arg is an array for string given during command line.
What are the differences between == and .equals() ?
Or
what is difference between == and equals
Or
Difference between == and equals method
Or
What would you use to compare two String variables – the operator == or the method
equals()?
Or
How is it possible for two String objects with identical values not to be equal
under the == operator?
The == operator compares two objects to determine if they are the same object in
memory i.e. present in the same memory location. It is possible for two String
objects to have the same value, but located in different areas of memory.
== compares references while .equals compares contents. The method public boolean
equals(Object obj) is provided by the Object class and can be overridden. The
default implementation returns true only if the object is compared with itself,
which is equivalent to the equality operator == being used to compare aliases to
the object. String, BitSet, Date, and File override the equals() method. For two
String objects, value equality means that they contain the same character
sequence. For the Wrapper classes, value equality means that the primitive values
are equal.
public class EqualsTest {
public static void main(String[] args) {
String s1 = “abc”;
String s2 = s1;
String s5 = “abc”;
String s3 = new String(“abc”);
String s4 = new String(“abc”);
System.out.println(“== comparison : ” + (s1 == s5));
System.out.println(“== comparison : ” + (s1 == s2));
System.out.println(“Using equals method : ” + s1.equals(s2));
System.out.println(“== comparison : ” + s3 == s4);
System.out.println(“Using equals method : ” + s3.equals(s4));
}
}
Output
== comparison : true
== comparison : true
Using equals method : true
false
Using equals method : true
What if the static modifier is removed from the signature of the main method?
Or
What if I do not provide the String array as the argument to the method?
Program compiles. But at runtime throws an error “NoSuchMethodError”.
Why oracle Type 4 driver is named as oracle thin driver?
Oracle provides a Type 4 JDBC driver, referred to as the Oracle “thin” driver.
This driver includes its own implementation of a TCP/IP version of Oracle’s Net8
written entirely in Java, so it is platform independent, can be downloaded to a
browser at runtime, and does not require any Oracle software on the client side.
This driver requires a TCP/IP listener on the server side, and the client
connection string uses the TCP/IP port address, not the TNSNAMES entry for the
database name.
- See Also……