Java input string readline

Java input string readline

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Java input string readline

• Introduction to Java
• The complete History of Java Programming Language
• C++ vs Java vs Python
• How to Download and Install Java for 64 bit machine?
• Setting up the environment in Java
• How to Download and Install Eclipse on Windows?
• JDK in Java
• How JVM Works – JVM Architecture?
• Differences between JDK, JRE and JVM
• Just In Time Compiler
• Difference between JIT and JVM in Java
• Difference between Byte Code and Machine Code
• How is Java platform independent?

• Decision Making in Java (if, if-else, switch, break, continue, jump)
• Java if statement with Examples
• Java if-else
• Java if-else-if ladder with Examples
• Loops in Java
• For Loop in Java
• Java while loop with Examples
• Java do-while loop with Examples
• For-each loop in Java
• Continue Statement in Java
• Break statement in Java
• Usage of Break keyword in Java
• return keyword in Java

• Object Oriented Programming (OOPs) Concept in Java
• Why Java is not a purely Object-Oriented Language?
• Classes and Objects in Java
• Naming Conventions in Java
• Java Methods
• Access Modifiers in Java
• Java Constructors
• Four Main Object Oriented Programming Concepts of Java
• Inheritance in Java
• Abstraction in Java
• Encapsulation in Java
• Polymorphism in Java
• Interfaces in Java
• ‘this’ reference in Java

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Java input string readline

«Но System.in и BufferedReader не совместимы друг с другом, поэтому мы используем переходник – еще один объект InputStreamReader» в данном случае под переходником имеется в виду шаблон Адаптер

Может, стоило для начала объяснить что такое объекты и классы для того чтобы оперировать этими понятиями, так как на данный момент мы изучили только переменные и методы.

Непонятно: говориться что в System.in храниться объект класса InputStream. Но InputStream это абстрактный класс у него не может быть объектов как так-то?

 BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); 

100% после прочтения этой бесполезной лекции, вы потеряли нить, зачем это все, посмотрите видеоролик, там очень доступно объясняют про то, как считывается поток вводных данных, что вообще такое поток и т.д Я считаю, что проектировщики плана обучения должны обязательно внести дополнения в эту лекцию, раз они начали здесь уже задвигать про ввод данных, это просто must have. Непонимание этой вещи вредит здоровью хуже, чем курение, наркотики и виски без льда.

не пользуйтесь Scanner-ом. у него есть 2 метода 1 — next() 2 — nextLine() они оба читают строку(но первый читает 1 слово, а 2 строку целиком) и в этом как раз загвоздка. Там дальше по заданию нужно будет считать строку и число и в этот момент вас ждет неприятный сюрприз: после считывания строки методом nextLine() у вас считывание числа не будет(программа завершится), а ошибку найти будет очень не просто. Многие наступали на эти грабли. Так что учите BufferedReader, как только поймете как составляются цепочки проблем с вводом данных дальше не будет.

Либо я дебил, либо лыжи не едут. Видеоурок вообще не о чем, как и лекция. Не представляю как бы я решал задачу в следующей лекции, если бы не наткнулся на «Java Syntax Pro 2 уровень, 5 лекция». Чтобы вы понимали, сейчас мы находимся на лекциях для начинающих и нормальное объяснение я нашел только на лекции уровня про. Плюс я не очень понимаю зачем нужно проходить то, что в реальной практике никогда не будет нужно?? «Использовать Scanner довольно удобно, но от этого не очень много пользы. Дело в том, что в будущем (и в учебе, и на работе) ты будешь часто использовать объекты BufferedReader и InputStreamReader и очень-очень редко объект типа Scanner. В данной ситуации он удобен, но в будущем толку от него мало. Так что мы пользоваться им не будем.»

я 20 минут пытался понять какого-то дядю, который объяснял кое как или его выступление было вырвано из контекста других лекций. но потом мне говорят, что этот сканер мне не надо. а нужен какой-то буфер, который работает только с каким-то костылем. (((

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String Input in Java

With the help of the I/O package, Java has several Streams that help the user in performing all the input-output activities. These streams support all types of objects, data types, characters, and so on.

For taking string input we can make use of various methods like using Scanner class, BufferedReader class, and Command Line argument.

How to Take String Input in Java ?

Input and Output are one of the most important parts of learning any programming language. Java has a various number of I/O Streams that help the user in performing all the input-output activities, taking string input from the user can be done using these I/O streams. Further in this article, we will discuss all those approaches that are needed to be followed for taking string input.

Method — 1 : By Using Java Scanner Class

The Scanner class is provided by the java.util package and is used to take input from the user. The Scanner class has the following methods that help us to take input from the user :

For using the Scanner class, we have to import the Scanner Class in our code by using the following syntax :

Now let’s see how these methods help us to take string input in Java.

Scanner.nextLine() Method

The Scanner class’s nextLine() method is used to take string input from the end user. nextLine() method is contain java.util.Scanner class. This method reads text until it reaches the end of the line. It moves the cursor to the next line after reading the line.

The skipped line is returned by the nextLine() method. It doesn’t take any parameters. When the nextLine() method can’t find a line, it throws a NoSuchElementException. If the scanner class is closed, it also throws an IllegalStateException.

Now let’s take a look at an example of the nextLine() method :

In this example, we are importing the scanner class using the nextLine() method followed by System.in standard input stream

In this example, we are showing the case when this method throws NoSuchElementException.

We haven’t provided any std input to our java program, so it will throw NoSuchElementException.

Scanner.next() Method

The Scanner class’s next() method in Java is used to read the input before the whitespace is detected. next() method is unable to read two words separated by whitespace. After reading the input, it keeps the pointer in the same line.

Next complete string value is returned by next() method. It doesn’t take any parameters. When the next() method can’t find string value, it throws a NoSuchElementException. If the scanner class is closed, it also throws an IllegalStateException.

Now let’s take a look at an example of the next() method :

In this example, we are importing the scanner class for using the next() method followed by System.in standard input stream

In this example, we are showing the case when this method throws NoSuchElementException.

We haven’t provided any std input to our java program, so it will throw NoSuchElementException.

Difference Between Scanner.nextLine() and Scanner.next()

The key difference between the nextLine() and next() method is that the next() method gets terminated when whitespace is encountered, whereas the nextLine() method terminates only when enter is pressed and next line is reached.

Method — 2 : By Using Java BufferedReader Class

The BufferedReader class is provided by the java.io package and is used to read the stream of characters, BufferedReader accepts the InputStreamReader class as the parameter for its execution.

Some basic differences between Scanner class and BufferedReader class :

• BufferedReader is synchronous while the Scanner is not. So, BufferedReader should be used if we are working with multiple threads.
• BufferedReader has a significantly larger buffer memory than Scanner.
• BufferedReader is slightly faster than the scanner since the scanner parses the input data, whereas BufferedReader reads a sequence of letters.

BufferedReader class has the readLine() method for taking string input from the user. readLine() method reads a single line at a time.

The readline() method returns the line that the user has entered. Now let’s take a look at an example of how the BufferedReader class is used for taking string input.

In this example, we are using BufferedReader with InputStreamReader for the standard IO stream, also BufferedReader must be used inside the try-catch block in case of exceptions.

Method — 3 : By Using the Command Line Arguments

In Java programs, we can pass the command line argument in the main method of the driver program.

String args[] is a string array that takes a line as an input. So, we can pass a string as an argument to the main method and can fetch its value and use it.

In this example, we have used the command line argument using the args[] array and used its value for displaying the string output.

Command Line Argument :

Conclusion

• Java has several Streams that help the user in performing all the input-output activities.
• String input can be achieved using Scanner class, BufferedReader class, and Command-line Arguments
• The Scanner class is provided by java.util package and uses the following methods for string input :
  • Scanner.nextLine() :
    This method reads text until it reaches the end of the line.
  • Scanner.next() :
    This method reads the input before the whitespace is detected.

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