Monday, 13 May 2013

Core JAVA Basics


CORE  JAVA:-
1.       Overview of Java
     a) Introduction to java
     b) Fundamentals of java
2.Classes, Objects, Methods
3. Arrays & Strings
4. Interfaces
5. Packages (Putting Classes Together)  
6. Multithreaded Programming
7. Applet Programming
8. Managing Errors and Exceptions
9. Graphics Programming
10. Managing Input/Output Files in java










Domain:-Overview of java
Sub domain:-Introduction to java
Question 1
 When and who invented java?
Answer
 Java is developed by Sun Microsystems of USA in 1991.
Question 2
Why is java known as platform-neutral language?
Answer
 It is so because java is not tied to any particular hardware or operating system. Programs developed in java can be executed anywhere on any system.
Question 3
How is java more secured than other languages?
Answer
 It is so because java systems not only verify all memory access but also ensure that no viruses are communicated with an applet. The absence of pointers in java ensures that programs cannot gain access to memory locations without proper authorization.
Question 4
 What is the difference between java and C?
Answer
Java
1.It doesn’t have C unique statement keywords sizeof,andtypedef.
2.It doesn’t have data types struct and union.
3.It doesn’t support an explicit pointer type.
4.It adds labelled break and continue statements.
5.It doesn’t have a preprocessor.
C
1.It contains the unique keywords sizeof, and tyedef.
2.It contains data types struct and union.
3.It support an explicit pointer type.
4.It doesn’t have break and continue statements.
5.It have preprocessor.




Question 5
 What is the difference between Java and C++?
Answer
Java
C++
1.       It doesn’t support operator overloading.
2.       It doesn’t have template classes.
3.       It doesn’t have multiple inheritance.
4.       It doesn’t support global variables.
5.       It doesn’t use pointers.
6.       It uses finalize () function.
7.       There are no header files in java.
1.       It supports operator overloading.

2.       It has template classes.
3.       It has multiple inheritance.
4.       It supports global variables.
5.       It uses pointers.
6.       It uses destructor () function.
7.       It has header files.

Question 6
Why do we need import statement in java?
Answer
It is because using import statements we can have access to classes that are part of other named package.
Question 7
 What is the task of main () method in a java program?
Answer
The main method creates objects of various classes and establishes communication between them. On reaching the end of main, the program terminates and the control passes back to the operating system.
Question 8
 What are separators? What are the various separators used in java?
Answer
 Separators are symbols used to indicate where groups of code are divided and arranged. They basically define the shape and function of our code.
Java includes six types of separators:-
§  Parentheses ()
§  Braces {}
§  Brackets []
§  Semicolon ;
§  Comma ,
§  Period

Question 9
 What are command line arguments? How are they useful?
Answer
 They are the parameters that are supplied to the application program at the time of invoking it for execution. They are useful as we make like our program to act in a particular way depending on the input provided at the time of execution which is achieved by command line arguments.
Question 10
 Java is a freeform language. Comment.
Answer
It is a freeform language as we need not have to indent any lines to make the program work properly. Also java system does not care where on the line we begin typing.
Question 11
 List the features of java?
Answer
Java has the following features:-
§  Simple and powerful
§  Secure
§  Portable
§  Object-oriented
§  Robust
§  Multithreaded
§  Architecture-neutral
§  Interpreted and High performance
§  Distributed
§  Dynamic
Question 12
What are the newly added features in java 2?
Answer
The following are the newly added features in java 2:-
§  Swing
§  Collections framework
§  Various tools such as javac, java and javadoc have been enhanced.
§  Just-In-Time (JIT) compiler
§  Policy files
§  Digital certificates
§  Advanced features for working with shapes, images and text.
§  Various security tools
§  The user can now play audio files such as MIDI, AU, WAV and RMF files using java programs.
Sub domain:-Fundamentals of java
Question 13
What is type casting? Why is it required in programming?
Answer
The process of converting one data type to another is called casting.
It is required because we often encounter situations where there is a need to store a value of one type into a variable of other type. Casting is often necessary when a method returns a type different than the one we require.
Syntax:-
           Type variable1 = (type) variable2;
Question 14
What are wrapper classes? What is their use?
Answer
Wrapper classes are provided for the primitive data types in order to use these types as objects.   The wrapper classes for the primitive data types have the same name as the primitive type, but with the first letter capitalized. The advantage of using wrappers is that when an object is passed to a method, the method is able to work on the object itself. Also the user can derive his/her own classes from java’s built-in wrapper classes.
Question 15
What is a literal? What are the difference types of literals?
Answer
A literal represents a value of a certain type where the type describes the behavior of the value. The different types of literals are:-
§  Number literals
§  Character literals
§  Boolean literals
§  String literals


Question 16
What is a variable? What are the different types of variables?
Answer
Variables are locations in the memory that can hold values. Java has three kinds of variables namely,
§  Instance variable
§  Local variable
§  Class Variable
Local variables are used inside blocks as counters or in methods as temporary variables. Once the block or the method is executed, the variable ceases to exist. Instance variables are used to define attributes or the state of a particular object. These are used to store information needed by multiple methods in the objects.
Domain: -Classes,Objects, Methods
Question 17
What is Collection API?
Answer
The Collection API is a set of classes and interfaces that support operation on collections of objects. These classes and interfaces are more flexible, more powerful, and more regular than the vectors, arrays, and hash tables if effectively replaces.
Example of classes: Hash Set, Hash Map, Array List, Linked List, Tree Set and Tree Map.
Example of interfaces: Collection, Set, List and Map.
Question 18
Is Iterator a Class or Interface? What is its use?
Answer
Iterator is an interface which is used to step through the elements of a Collection.
Question 19
What is similarities/difference between an Abstract class and Interface?
Answer
Differences are as follows:
Interfaces provide a form of multiple inheritances. A class can extend only one other class. Interfaces are limited to public methods and constants with no implementation. Abstract classes can have a partial implementation, protected parts, static methods, etc.
A Class may implement several interfaces. But in case of abstract class, a class may extend only one abstract class. Interfaces are slow as it requires extra indirection to  find corresponding method in in the actual class. Abstract classes are fast.
Similarities:
Neither Abstract classes or Interface can be instantiated.
Question 20
How to define an Abstract class?
Answer
A class containing abstract method is called Abstract class. An Abstract class can't be instantiated.
Example of Abstract class:
abstract class testAbstractClass {
protected String myString;
public String getMyString() {
return myString;
}
public abstract string anyAbstractFunction();
}
Question 21
When do we create member of a class static?
Answer
Static variables are used when we want to have a variable common to all instances of a class. Java creates only one copy for static variable which can be used even if the class is never actually instantiated.
Question 22
Describe the syntax of single inheritance in java?
Answer
Syntax:-
Class subclassnameextendssuperclassname
             {
                  Variables declaration;
                  Methods declaration;
            }




Question 23
Describe method overloading and method overriding?
Answer
The process in which methods have same name, but different parameter lists and different definitions is called method overloading. It is used when objects are required to perform similar tasks but using different input parameters. These are the forms of Static polymorphism.
Domain:-Arrays and Strings
Question 24
What is string Buffer?
Answer
It is a peer class of string that provides much of the common functionality of strings. Strings represent fixed-length character sequences. String Buffer represents varied length character sequences. String buffer may have characters and substrings inserted in the middle, or appended at the end. The complier automatically creates a String Buffer to evaluate certain expressions, in particular when the overloaded operators + and += are used with string objects.
Question 25
What are arrays?
Answer
An array is an object that stores a list of items. Each slot in an array holds individual elements. An array should be of a single type, comprising of integers, strings and so on.
Question 26
What is the use of hash table?
Answer
A hash table stores information using a special calculation on the object to be stored. A hash code is produced as a result of the calculation. The hash code is used to choose the location in which to store the object.




DOMAIN:-INTERFACES
Question 27
How to define an Interface in Java?
Answer
In Java Interface defines the methods but does not implement them. Interface can include constants. A class that implements the interfaces is bound to implement all the methods defined in Interface.
Example of Interface:

public interface sampleInterface {
public void functionOne();

public long CONSTANT_ONE = 1000;
}
Question 28
What is the difference between class and interface in java?
Answer
The difference between interface and java are-
CLASS
INTERFACE
1. The members of a class can be constant or variables
1. The members of an interface are always declared as constant, i.e.., their values are final
2. The class definition can contain the code for each of its methods
2. The methods in interface are abstract in nature i.e. there is no code associated with them.
3. It can be instantiated by declaring objects
3. It cannot be used to declare objects
4. It can use various specifiers like public,private,protected
4. It can only use the public access specifier

Question 29
What are the similarities between interfaces and classes?
Answer
§  The similarities between interfaces and classes are-
§  An interface is basically a kind of class.
§  Like classes, an interface contains methods and variables.
§  Both can be inherited.


Domain:-Packages (Putting Classes Together)
Question 30
What is a package?
Answer
Packages are java’s ways of grouping a variety of classes and /or interfaces together. They are containers for classes that are used to compartmentalize the class name space. Packages are stored in a hierarchical manner and are explicitly imported into new class definitions.
Question 31
What is static import? How is it useful?
Answer
It is another language feature introduced with the J2SE 5.0 release. This feature eliminates the need of qualifying a static member with the class name. The static import declaration is similar to that of import. Also static import statement used to import static members from classes and use them without qualifying the class name.
Domain:-Multithreaded Programming
Question 32
What is a thread?
Answer
A thread is similar to a program that has a single flow of control. It has a beginning a body, and an end, and executes commands sequentially.
Question 33
Define multithreaded program.
Answer
A program that contains multiple flows of control is known as multithreaded program.
Question 34
Define concurrency.
Answer
The ability of a language to support multithreads is referred to as concurrency.


Question 35
Define lightweight threads.
Answer
Threads in java are subprograms of a main application program and share the same memory space are known as lightweight threads.
Question 36
What is the difference between multithreading and multitasking?
Answer
The difference between multithreading and multitasking are-
Multithreading
Multitasking
1.It is a programming concept in which a program or a process is divided into two or more subprograms or threads that are executed at the same time in parallel.
1. It is an operating system concept in which multiple tasks are performed simultaneously.
2.It supports execution of multiple parts of a single program simultaneously.
2. It supports execution of multiple programs simultaneously.
3. The processor has to switch between different parts or threads of a program.
3. The processor has to switch between different programs or processes.
4. It is highly efficient.
4. It is less efficient in comparison to multithreading.
5. A thread is smallest unit in multithreading.
5 .A program or process is the smallest unit in a multitasking environment.
6. It helps in developing efficient programs.
6. It helps in developing efficient operating systems.
7. It is cost- effective  in case of context switching.
7. It is expensive in case of context switching

Question 37
What are the ways to create threads?
Answer
A new thread can be created in two ways:-
1. By creating a thread class: Define a class thread that extends Thread class and override its run () method with the code required by the thread.
2. By converting a class to a thread: Define a class that implements Runnable interface. The      Runnable interface has only one method, run (), that is to be defined in the method with the code to be executed by the thread.

Question 38
How do we start a thread?
Answer
To Start a thread we must write the following code:-
ClassnameaThread = new classname ();
aThread.start ( );
Question 39
What are the methods by which we may block threads?
Answer
A thread can be temporarily suspended or blocked from entering into the runnable and subsequently running state by using either of the following thread methods:-
1. sleep ()          // blocked for a specified
2. suspend ()   // blocked until further orders
3. wait ()          // blocked until certain condition occurs
Question 40
What is the difference between suspending and stopping a thread?
Answer
Suspending a thread means that thread can be revived by using the resume () method. This approach is useful when we want to suspend a thread for some time due to certain reason, but do not want to kill it.
Stopping a thread causes the thread to move to the dead state. The stop () method may be used when the premature death of a thread is desired.
Question 41
How do we set priorities for thread?
Answer
Java permits us to set the priority of a thread using the setPriority () method as follows:
Thread Name.SetPriority (int Number);
The intNumber is an integer value to which the thread’s priority is set. The Thread class defines several priority constants:
MIN_PRIORITY =1
NORM_PRIORITY =5
MAX_PRIORITY =10
The int number may assume one of these constants or any value between 1 and 10. The default setting is NORM_PRIORITY.
Question 42
Describe the complete life cycle of a thread.
Answer
During the life time of a thread, there are many states it can enter. They include:
1. Newborn state: When we create a thread object, the thread is born and is said to be in newborn     state.
2. Runnable state: It means that the thread is ready for execution and is waiting for the availability of the processor.
3. Running state: It means that the processor has given its time to the thread for its execution.
4. Blocked state: It is when thread is prevented from entering into the runnable state and subsequently the running state.
5. Dead state: It is the last stage of the thread. In this stage the thread is killed or it has completed executing its run () method.
Question 43
Define time-slicing.
Answer
The process of assigning time to threads is known as time-slicing.
Question 44
What is synchronization? When do we use it?
Answer
Synchronization is a process of controlling the access of shared resources by the multiple threads
such a manner that only one thread can access one resource at a time. In non-synchronizedmultithreaded application, it is possible for one thread to modify a shared object while another thread is in the process of using or updating the object's value. Synchronization prevents such type of data corruption.
We use this when a situation such as one thread may try to read a record from a file while another is still writing to the same file arises.


Domain:-Applet Programming
Question 45
What is an applet?
Answer
Applets are small java programs that are primarily used in internet computing. They can be transported over the internet from one computer to another and run using the Applet viewer or any web browser that supports java. It can perform arithmetic operations, display graphics, play sounds, accept user input, create animation, and play interactive games.
Question 46
What is a local applet?
Answer
An applet developed locally and stored in a local system is known as alocal applet. When a web page is trying to find as a local applet, it does not need to use internet connection and therefore the local system does not use the internet connection. It simply searches the directories in the local system and locates and loads the specified applet.
Question 47
What is a remote applet?
Answer
A remote applet is that which is developed by someone else and stored on a remote computer connected to the internet. If our system is connected to the internet, we can download the remote applet onto our system via at the internet and run it.
Question 48
How do applets differ from application programs?
Answer
Applets differ from application programs in the following ways-
§  Applets do not use the main () method for initiating the execution of the code. Applets, when loaded, automatically call certain methods of Applet class to start and execute the applet code
§  Unlike stand-alone applications, applets cannot be run independently. They are run from inside a web page using a special feature known as HTML tag
§  Applets cannot read from or write to the files in the local computer
§  Applets cannot communicate with other servers on the network
§  Applets cannot run any program from the local computer
§  Applets are restricted from using libraries from other languages such as C or C++

Question 49
What are the various sections of Web Page?
Answer
A web page is basically made up of text and HTML tags that can be interpreted by a web browser or an applet viewer. A web page is marked by an opening HTML tag <HTML> and a closing HTML tag<\HTML> and is divided into the following three major sections-
1.       Comment section ( optional )
2.       Head section ( optional )
3.       Body section
Comment section:-This section contains comments about the web page.
Header section: - The head section is defined with a starting <HEAD> tag and a closing <\HEAD> tag. This section usually contains a title for the web page.
Body section:-This section contains the entire information about the web page and its behaviour. We can set u many options to indicate how our page must appear on the screen (like color, location, sound etc.) It contains applet tag also.
Question 50
How many arguments can be passed to an applet using <PARAM> tags?
Answer
We can supply user-defined parameters to an applet using <PARAM> tags. Each <PARAM> tag has a name attribute such as color, and a value attribute such as red. Inside the applet code, the applet can refer to that parameter by name to find its value.
Question 51
Describe the different stages in the life cycle of an applet.
Answer
The stages in the life cycle of an applet are-
1. Born or initialization state
2. Running state
3. Idle state
4. Dead or destroyed state
Born or initialization state: - Applet enters the initialization state when it is first loaded. This is achieved by calling the init () method of Applet class. The applet is born. At this stage, we may do the following if required
a) Create objects needed by the applet
b) Set up initial values
c) Load images or fonts
d) Set up colors
The initialization occurs only once in the applet’s life cycle. To provide any of the behaviours ,we must override the init() method.
Running state: - Applet enters the running state when the system calls the start( ) method of Applet Class. This occurs automatically after the applet is initialized. Starting can also occur if the Applet is already in ‘stopped” ( idle) state. For example, we may leave the web page containing the applet temporarily to another page and return back to the page. This again starts the applet running. Note that, unlike init( ) method, the start( ) method may be called more than once. We may override the start( ) method to create a thread to control the applet.
Idle or stopped state: - An applet becomes idle when it is stopped from running. Stopping occurs automatically when we leave the page containing the currently running applet. We can also do so by calling the stop( ) method explicitly. If we use a thread to run the applet, then we must use stop( ) method to terminate the thread. We can achieve this by overriding the stop( ) method;
Dead state: - An applet is said to be dead when it is removed from memory. This occurs automatically by invoking the destroy( ) method when we quit the browser. Like initialization, destroying stage occurs only once in the applet’s life cycle. If the applet has created any resources, like threads, we may override the destroy( ) method to clean up these resources.
Question 52
What is event handling?
Answer
Event handling is a mechanism that is used to handle events generated by applets. An event could be the occurrence of any activity such as a mouse click or a key press. In java, events are regarded as method calls with a certain task performed against the occurrence of each event.
Question 53
Name some of the key events?
Answer
Some of the key events are:
1.ActionEvent is triggered whenever a user interface element is activated, such as selection of a menu item.
2. ItemEvent is triggered at the selection or deselection of an itemized or list element, such as checkbox.
3. TextEvent is triggered when a text field is modified.
4. WindowEvent is triggered whenever a window – related operation is performed, such as closing or activating a window.
Question 54
Define Event Listeners.
Answer
The event listener object contains methods for receiving and processing event notifications sent by the source object. These methods are implemented from the corresponding listener interface contained in the java.awt.event package.
Question 55
Define Event Classes.
Answer
All the events in java have corresponding event classes associated with item. Each of these classes is derived from one single super class, i.e., EventObject. It is contained in the java.util package. The EventObject class contains the following two important methods for handling events:
1.getSource(): Returns the event source.
2.toString (): Returns a string containing information about the event source.
Question 56
How is java’s coordinate system organized?
Answer
Java’s coordinate system has the origin (0, 0) in the upper–left corner. Positive x values are to the right, and positive y values are to the bottom. The values of coordinates x and y are in pixels.
Question 57
Describe the arguments used in the method drawRoundRect( ).
Answer
The drawRoundRect() method takes 6 arguments:-The first two represent the x and y coordinates of the top left corner of the rectangle,and the next two represent the width and the  height of the rectangle and the remaining two represent the width and height of the angle of corners.




Question 58
What is AWT?
Answer
The Abstract Windowing Toolkit ( AWT) IS AN APL that is responsible for building the Graphical User Interface ( GUI). It is a part of java Foundation Classes (JFC). AWT includes a rich set of user interface components, a powerful event handling model, graphics and image tools, layout managers and support for data transfer using cut and paste through clipboards. AWT also supports JavaBeans architecture. Every AWT component is a simple bean. The java.awt package contains all classes for creating user interfaces and for painting graphics and image.
Question 59
What is Component?
Answer
Component class is the super class to all the class to all the other classes from which various GUI elements are realized. It is primary responsible for effecting the display of a graphic object on the screen. It also handles the various keyboard and mouse events of the GUI application.
Question 60
What is Container?
Answer
The Container object contains the other awt components. It manages the layout and placement of the various awt components within the container. A container object can contain other containers objects as well; thus allowing nesting of containers.
Question 61
What is Window?
Answer
The Window object realizes a top-level window but without any border or menu bar. It just specifies the layout of the window. A typical window that you would want to create in your application is not normally derived from the Window class but from its subclass, i.e., Frame.
Question 62
What is Panel?
Answer
The super class of applet, Panel represents a window space on which the application’s output is displayed. It is just like a normal window having no border, title bar, menu bar, etc. A panel can contain within itself other panels as well.
Question 63
What is Frame?
Answer
The Frame object realizes a top-level window complete with border and menu bar. It supports common window-related events such as close, open, activate, deactivate, etc. Almost all the programs that we created while discussing applets and graphics programming used one or more classes of the awt packaged.
Question 64
Describe the arguments used in the method drawRoundRect ().
Answer
The arguments used are the first two represent the x and y coordinates of the top left corner of the rectangle and the next two represent the width and height of the rectangle and the remaining two represent  the width and height of the angle of the corners.
SUBDOMAIN:-Managing Errors And Exceptions
Question 65
What is an Error?
Answer
An error may produce an incorrect output or may terminate the execution of the program abruptly or even may cause in the program will not terminate or crash during execution.
Question 66
What are the types of Errors?
Answer
Errors may broadly be classified into two categories:
1. Compile-time errors:- All syntax errors will be detected and displayed by the java compiler and therefore these errors are known as compile-time errors. Whenever the Compiler displays an error, it will not create the class file. It is therefore necessary that we fix all the errors before we can successfully compile and run the program.
2. Run-time errors:- Sometimes, a program may compile successfully creating the .class file but may not run properly. Such programs may produce wrong results due to wrong logic or may terminate due to errors such as stack overflow. This is called Run-time errors.



Question 67
Define exception.
Answer
An exception is a condition that is caused by a run-time error in the program. When the java interpreter encounters an error such as dividing an integer by zero, it creates an exception object and throws it (i.e. informs us that an error has occurred. The purpose of exception handling mechanism is to provide a means to detect and report an “exceptional circumstance” so that appropriate action can be taken.
Question 68
How is Exceptions in java categorized?
Answer
Exceptions in java can be categorised into two types:
1.Checked exceptions: These exceptions are exceptions are explicitly handled in the code itself with the help of try-catch blocks. Checked exceptions are extended from the java.lang.Eception class.
2. Unchecked exceptions: These exceptions are not essentially handed in the program code; instead the JVM handles such exceptions. Unchecked exceptions are extended from the java.lang.RuntimeException class.
Subdomain:-Managing Input/output Files in Java
Question 69
What is Persistent data?
Answer
Data stored in files is often called Persistent data.
Question 70
What is Object serialization?
Answer
The process of reading and writing objects is called object serialization.
Question 71
What is a file?
Answer
A file is a collection of related records placed in a particular area on disk.

Question 72
What is a record?
Answer
A record is composed of several fields and a field is a group of characters.
Question 73
What is file processing?
Answer
Storing and managing data using files is known as file processing which includes tasks such as creating files, updating files and manipulation of data.
Question 74
What is a stream?
Answer
A stream in java is a path along which data flows (like a river or a pipe along which water flows). It has a source (of data) and a destination (for that data).
Question 75
How is the concept of steams used in java?
Answer
The concept of sending data from one stream to another (like one pipe feeding into another pipe) has made streams in java a powerful tool for file processing.
Question 76
What are input and output streams?
Answer
Java streams are classified into two basic types, namely, input stream and output stream. An input stream extracts (i.e. reads) data from the source (file) and sends it to the program. Similarly, an output stream takes data from the program and sends (i.e. writes) it to the destination (file).
Question 77
What is stream class? How are the stream class classified?
Answer
The java.io package contains a large number of stream classes that provide capabilities for processing all types of data. These classes may be categorized into two groups based on the data type on which they operate.
1.Byte stream classes that provide support for handling I/O operations on bytes.
2. Character stream classes that provide support for managing I/O operations on characters.
Question 78
Describe the major tasks of input and output stream classes.
Answer
The super class InputStream is an abstract class, and, therefore, we cannot create instances of this class. Rather, we must use the subclasses that inherit from this class. The InputStream class defines methods for performing input functions such as
1 Reading bytes
2 Closing streams
3 Marking Positions in streams
4 Skipping ahead in a stream
5 Finding the number of bytes in a stream
Outputstream is an abstract class and therefore we cannot instantiate it. The several subclasses of the OutputStream can be used for performing the output operations.
The Ouptputstream includes methods that are designed to perform the following tasks:
1 Writing bytes
2 Closing streams
3 Flushing streams
Question 79
What is reader stream class?
Answer
Reader stream classes are designed to read character from the files. The Reader class contains methods that are identical to those available in the Inputstream class, except reader is designed to handle characters.
Question 80
What is writer stream classes?
Answer
The writer class is an abstract class which acts as a base class for all the other writer stream classes.

Question 81
What is RandomAccessFile?
Answer?
The RandomAccessFile enables us to read and write bytes, text and java data types to any location in a file (when used with appropriate access permissions). This class extends object class and implements DataInput and Dataoutput interfaces. This forces the RandomAccessFile to implement the methpods described in both these interfaces.
Question 82
What is Stream Tokenizer?
Answer
The class Stream Tokenizer, a subclass of object can be used for breaking up a stream of text from an input text file into meaningful pieces called tokens. The behaviour of the Stream Tokenizer class is similar to that of the String Tokenizer class (of java.util Package) that breaks a string into its component tokens.
Question 83
What is file class?
Answer
The java.io package includes a class known as the File class that provides support for creating files and directories. The class includes several constructors for maintaining the file objects. This class also contains several methods for supporting the operations such as
1 Creating a file
2 Opening a file
3 Closing a file
4 Deleting a file
5 Getting a name of a file
6 Getting the size of a file
7 Checking the existence of a file
8 Renaming of a file
9 Checking whether the file is writable
1o Checking whether the file is readable
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