java contd..

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.