DS-Java-Training-Programs/java notes.txt at main · vedangi163/DS-Java-Training-Programs · GitHub

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// In D drive, riun eclipse.exe

1. In local scope, we must have initialize the value before using it.
   but for instance variable, you do not need for anythoimg


HW
static method and data members
why main static access non-access members
static is associated with data members and not local members

final - variable, method and class

Abstract -
1. An abstract class not instantiated, but reference can be created but it is null and eventually we cannot call non-abstract method on null
2. AC contain non abstract methods also
3. Abstract method do not have body
4. A class must be abstract if it has abstract method in it
5. We can bypass thye abstract method by making class as abstract


Package
organize the files
java.lang ===> java/lang
. used for directory hierachy


constructor provided by compiler is default & explicire;ly defined by user called explicit constructor


protected -> only by extends in child class

if throw is used within mwthod/constructor, method/constructor must used throws in case of checked exception
All exceptions are checked except RuntimeException


No need to catch runtime/unchecked exceptions and no need to use throws in unchecked exceptions
But checked exceptions must have to catch & need to throws from the methos


For databse connection:
1. Install databse
2. Install drivers of database
3. Write a java code to connect to the databse


Driver:
1. Know your driver
2. Register the driver
3.