Java Tutorial

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Java Loops

Java Do While Loop Java While Loop Java For Loop Java Enhanced For Loop

Java Programs

Java Basic Programs Factorial Program in Java Fibonacci Series Program in Java Prime Number Program in Java Palindrome Number Program in Java Armstrong Number Program in Java Anagram Program in Java Pattern Programs in Java Calculator Program in Java Leap Year Program in Java Addition Program in Java Number Pattern Programs in Java Star Pattern Programs in Java Package Program in Java Pyramid Program in Java Sorting Program in Java String Palindrome Program in Java Even Odd Program in Java For Loop Program in Java If Else Program in Java Switch Case Program in Java GCD Program in Java LCM Program in Java Hello Program in Java Matrix Program in Java Menu Driven Program in Java Series Program in Java Client Server Program in Java Swapping Program in Java Pig Latin Program in Java Tower of Hanoi Program in Java Recursion Program in Java Matrix Multiplication Program in Java Perfect Number Program in Java Classes and Objects in Java Example Programs String Programs in Java Array Programs in Java Constructor Program in Java Inheritance Program in Java Abstract class Program in Java Interface Program in Java Encapsulation Program in Java Polymorphism Program in Java Exception Handling Program in Java Multithreading Program in Java Thread Program in Java Collection Programs in Java ArrayList Program in Java Stack Program in Java Applet Program in Java Swing Program in Java JDBC Program in Java How to run Java program in command prompt How to run Java program in Eclipse

Java Sorting

Sorting Algorithms in Java Merge Sort in Java Quick Sort in Java Bubble Sort in Java Insertion Sort in Java Selection Sort in Java Heap Sort in Java Radix Sort in Java Topological Sort in Java Bucket Sort in Java Counting Sort in Java

Java OOPs Concepts

OOPs - Object Oriented Programming Objects and Classes in Java Java Naming Conventions Constructors in Java Java this keyword Java static keyword Inheritance in Java Aggregation in Java Java super keyword Constructor Chaining and Constructor Overloading Java Polymorphism Static and Dynamic Binding in Java Java Abstraction Abstract class in Java Interface in Java Difference between Abstract class and Interface Java final keyword Packages in Java Access Modifiers in Java Java Wrapper classes Java Numbers Java Characters Java Integer Java Boolean Java Arrays Java Command Line Arguments Java strictfp Keyword Java Math

Java Strings

Java Strings Java String Methods StringBuilder in Java StringBuffer in Java Java Regular Expressions StringBuffer vs StringBuilder String vs StringBuffer String vs StringBuilder String Manipulation in Java Java String Concatenation How to Reverse a String in Java String Array in Java How to Compare Two Strings in Java How to Concatenate Two Strings in Java Why String in Immutable in Java java.lang.NumberFormatException for Input String String Pool in Java Java Generate Random String How to take String Input in Java Java String Interview Questions

Java Exceptions

Exception Handling in Java Java try catch Java throw Java throws Difference between throw and throws Java finally Java Custom Exception Java Exception Propagation

Garbage Collection

Automatic Resource Management in Java Java Garbage Collection Java finalize() Java gc() Difference between final, finally and finalize

Multithreading

Multithreading in Java Process and Thread in Java Basic Terms in Multithreading Java Thread creation Thread Scheduler in Java Java Thread class DeadLock in Java

Java IO

Java IO Java Read File Java BufferedWriter Java InputStreamReader Java File Java Read File Line By Line Java FileOutputStream Jar File in Java

Serialization

Java Serialization Java transient

Networking

Java Network Programming Java Socket Programming Java URL Java URLConnection HttpURLConnection in Java Java InetAddress Java DatagramSocket and Java DatagramPacket

AWT

Java AWT

Swing

Swing in Java

Java Collections

Collections in Java Java List Interface ArrayList in Java LinkedList in Java Vector in Java Stack in Java ArrayList vs LinkedList in Java ArrayList vs Vector in Java Java Set Interface HashSet in Java LinkedHashSet in Java TreeSet in Java Java Queue Interface PriorityQueue in Java ArrayDeque in Java Java Map Interface HashMap in Java LinkedHashMap in Java TreeMap in Java Dictionary in Java Hashtable in Java Properties in Java Collections class in Java Java Comparable Java Comparator Comparable vs Comparator in Java

Java Generics

Generics in Java

Java Annotations

Annotations in Java

Java JDBC

Java JDBC Tutorial

Java Differences

Java vs JavaScript Python vs Java Kotlin vs Java Java vs C++ C# vs Java Static vs Non-static in Java C vs Java int vs Integer in Java Stack vs Heap in Java Java Array vs ArrayList

How to

How to run Java program How to set path in Java How to check the Java version in cmd How to install Java in Windows 10 How to run Java program in cmd How to call a method in Java How to sort an array in Java How to iterate HashMap in Java How to write Java program How to create an array in Java How to create a package in Java How to generate random numbers in Java How to input String in Java How to create thread in Java How to find length of String in Java How to sort a string in Java How to use scanner in Java How to achieve multiple inheritance in Java How to run Java program in Eclipse How to call a function in Java How to create array of objects in Java How to create custom exception in Java How to achieve abstraction in Java How to call static method in Java

Java 8 Features

Java 8 Features Lambda Expressions in Java Functional Interface in Java Streams in Java Java Base64 Encoding and Decoding Parallel Arrays Sort in Java

Java 9 Features

Java 9 Tutorial Java 9 Try With Resources Java 9 Interface Private Method

Java Servlet Tutorial

Java Servlets Tutorial

Java JSP Tutorial

Java JSP Tutorial

Hibernate Tutorial

Hibernate Tutorial

Spring Tutorial

Spring Tutorial

Spring MVC Tutorial

Spring MVC Tutorial

Jenkins Tutorial

Jenkins Tutorial

Java Math Methods

Math.abs() Math.acos() Math.addExact() Math.asin() Math.atan () Math.atan2() Math.cbrt() Math.ceil() Math.copysign() Math.cos() Math.cosh() Math.decrementExact() Math.exp() Math.expm1() Math.floor() Math.floorDiv() Math.floorMod() Math.getExponent() Math.hypot() Math.IEEEremainder() Math.incrementExact() Math.log() Math.log10() Math.log1p() Math.max() Math.min() Math.multiplyExact() Math.multiplyFull() Math.negateExact() Math.nextAfter() Math.nextDown() Math.nextUp() Math.pow() Math.random() Math.rint() Math.round() Math.scalb() Math.signum() Math.sin() Math.sinh() Math.sqrt() Math.subtractExact() Math.tan() Math.tanh() Math.toDegrees() Math.toIntExact() Math.toRadians() Math.ulp()

Java String Methods

toCharArray() copyValueOf() endsWith() equals() equalsIgnoreCase() format() getBytes() getChars() hashCode() indexOf() intern() isEmpty() join() lastIndexOf() length() replace() replaceAll() replaceFirst() split() startsWith() subSequence() substring() toLowerCase() toUpperCase() trim() valueOf()

Java Conversion

Java Convert String to int Java Convert int to String Java Convert String to long Java Convert long to String Java Convert String to float Java Convert float to String Java Convert String to double Java Convert double to String Java Convert String to Date Java Convert Date to String Java Convert String to Object Java Convert Object to String Java Convert String to char Java Convert char to String Java Convert int to long Java Convert long to int

Misc

Functional Interfaces in Java Singleton class in Java Awesome explanation of Strings in Java Object class in Java Static class in Java All the important string methods in Java String Handling Method in Java What are Array strings in Java Advantages and Disadvantages of Strings in Java Big Decimal class in Java Class definition in Java Char and String differences in Java Difference between String, StringBuffer and StringBuilder in java Replace character in string Java String Coding Interview Questions in Java What is String in Java? String isnullorempty in Java String Matches in Java Trim Method in String Java Bean class in Java Libraries in Java Arithmetic Operations on String in Java

Java Read File

Java provides its users with many ways of reading a file. To read a text file, you can use a FileReader, BufferedReader, or Scanner. Each utility offers something special for example, the BufferedReader provides data buffering for fast reads, and the Scanner provides analysis capabilities. The type of content in a file determines which file reader to use. Some methods are suited for faster implementation, and others are good at reading small file data. Some provide line-by-line read, while one of them reads file character by character. In the following article, we'll look at all of Java's ways to read files.

1. BufferedReader Class

To read text from a character-input stream, the class BufferedReader is utilized. It buffers characters to read input efficiently, including characters, arrays, or lines.

The buffer size is either determined by the user or by the default size, which can be used because it is large enough to handle most cases. It inherits the reader class using inheritance concepts. BufferedReader has two types of constructors, which are as follows:

  • BufferedReader( Reader in): This will utilize BufferedReader's default size.
  • BufferedReader (Reader in, int n): This will use the size specified by the user.
Java Read File

The above snippet of code is an example of how one can use BufferedReader to read contents from a file and print it.

In the first line, we have specified the path of the file. The file contains some text. We check whether the file is empty or not and then print the file's content. We can see files getting printed in the console as we run the program.

Java Read File
  • FileReader: It may seem that FileReader shares similarities with BufferedReader but has many differences. Unlike  BufferedReader,  it isn't buffered in any way. It reads data from a file and extracts characters.
    It is, on the whole, slower and less efficient than BufferedReader.
    FileReader has the following Constructors.
  • FileReader ( File file): It gets the file's name in the file instance.
  • FileReader(String fileName): First, it opens the file. If the file is not present in the specified path, then it will throw FileNotFoundException
Java Read File Java Read File

Unlike the BufferedReader, the text is printed word by word as FileReader extracts characters from a text file.

  • Scanner class: The Scanner class can also be used to read text from a text file. Following are the constructors provided by the Scanner class in JavaJava.
  • Scanner (File Source): This function reads data from a File object that represents a file.
  • Scanner (InputStream source): To read data from an InputStream, call this method.
  • Scanner (Path source): This method reads the file that the object specifies.
Java Read File Java Read File

Following is an implementation of the Scanner class.

There's another way to read the entire file. Instead of using a while loop, we can use the following code;-

sc.useDelimiter("\\Z")

It’s a java scanner class. This is used to set the delimiting pattern for the Scanner being used. For this case, the Scanner pattern is used. It returns the scanner object.

To better understand, let's take the comparison between BufferedReader, FileReader, and Scanner.

BufferedReader FileReader
It is buffered                                                     It is not buffered
It uses a buffer to read data.                            It reads data from a  file.  
It buffers the character.                                   It obtains characters from a file. 
Comparatively faster                                       Comparatively slower.
More efficient for reading files                       Comparatively less efficient.  
It can read a single character as well as the whole line.    At any given time, just one character can be read.
BufferedReaderScanner
It comes with a bigger buffer memory.It has a smaller buffer memory.
It is synchronous.                                                       It is not synchronous.   
It is comparatively faster.                                           It is comparatively slower. 
It should be used when we are working with multiple threads.                                                              It should be used when we are not working with multiple threads.  
  • Reading the whole file in a List: In Java 7, a convenient method for reading a file as lines of text was added. The method List<String> is used to do so. Bytes from the record are decoded into characters to use the desired charset. This approach guarantees that the record is closed while all bytes had been examined or an I/O error, or different runtime exception, is thrown.

Syntax

public static List readAllLines(Path path, Charset cs)throws IOException
Java Read File

In the above code, we have stored all the data of the file inside a list whose reference variable is read. Apple is the name of our file.

To print the data stored in the list, we have used a while loop, which first iterates over the list and then prints the data inside the list until the list doesn't get empty. When we run the program above, the following is the result we get.

Java Read File
  • Read a text file as String: This is the normal method for reading the entire file as a String in Java, with the caveat that the file must be small or medium in size. Unlike the above method, which stores the whole file data in  List, this method stores all the file's data in a  String.
Java Read File

The above code snippet has implemented the knowledge of reading the text file as a string. Apple is the name of our file, and as you can see from the above code, we have read all the data present inside the file name apple using String. And to print the data from files, we have just printed the String. Following is the result of our code.

Java Read File

Conclusion

As we have mentioned all the methods to read the file in JavaJava, one might get confused to implement. Even though we have mentioned the use case of almost every method, one might be looking for the best way to read a file. Mentioning one method as the best is quite tricky as it varies with what you need and what you are implementing.

While comparing all the file reading methods and analyzing their implementation, we can assume that; the fastest way to read a file is by implementing the concept of BufferedReader. It is fast enough to read millions of lines in a second with its implementation compared to other available methods.



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