Packages
Packages are created to group related classes/interfaces/other files.
- We generally group things to organize them better for locating them easily.
- Package creation – Create a new Java project say Facebook and group the Classes under various packages – view here
- Demonstrate – Accessing instances variables and methods from other class which is under the same package
- Demonstrate – Importing the Classes in the other packages while accessing the instance variables and methods created in the Classes which are under other packages
- Demonstrate – default and protected (within package and outside package)
- Demonstrate – Using * in the import statements to import all the classes in the package instead of importing a single class every time
Handling Files
- File is a predefined Class in Java
- Using File Class represent a file in Java, which is available outside the Project workspace.
- Using File Class represent a file in Java, which is available inside the Project workspace.
- Absolute Path
- Shortcut Path
- Representing a File and creating it
- File f = new File(“fileName.extension”);
- createNewFile()
- exists() method
- Representing a Folder and creating it
- File f = new File(“FolderName”);
- mkdir();
- exists() method
- Creating the file at the desired folder location
- File f2 = new File(f1,”fileName.extension”);
- File Methods
- isFile()
- isDirectory()
- delete()
- FileWriter
- write(String s)
- flush()
- close()
- FileReader
- read()
- close()
- BufferedWriter
- write(String s)
- newLine()
- flush()
- close()
- BufferedReader
- readLine()
- PrintWriter
- println()
- print()
- flush()
- close()
- We can use FileOuputStream for writing into the file and FileInputStream for reading from file.
- fos.write(textToBeWritten.getBytes());
- fos.flush();
- fis.read();
- (char)fis.read();
Collections Framework
Collection is a group of individual Objects.
- Array’s are fixed in sized, where as Collections are grow-able in size
- Though Collections Framework is a vast subject, we have to only learn the below for Selenium:
- ArrayList
- ArrayList is nothing but a re-sizable array and is not of fixed size
- Demonstrate an ArrayList which stores integer values and uses for loop to print those values
- Demonstrate an ArrayList which stores different types of values and uses for each loop to print those values
- Assigning the object of ArrayList class to Collection / List Interface – Demonstrate
- HashSet
- Unlike ArrayList, HashSet wont have index values and hence we cannot use for loop with HashSet
- Unlike ArrayList, HashSet stores the values in a random order
- Demonstrate HashSet which stores integer type of values and uses for each loop to print those values
- Assigning the object of HashSet class to Collection / Set Interface
- Iterator interface and iterator() method
- iterator() is a predefined method of Collection interface, who’s return type is Iterator interface
- hasNext() and next() are the predefined methods of the Iterator interface
- Demonstrate using Iterator and iterator() with ArrayList
- Demonstrate using Iterator and iterator() with HashSet
- HashMap
- Instead of storing the objects as a group of Objects, HashMap stores the objects in the form of key value pairs.
- Demonstrate a HashMap which stores different key value pairs and uses get() method to retrieve a value based on the provided key
- Demonstrate a HashMap which stores different key value pairs and uses for each loop to print those values
By,
Arun Motoori