Reading in from System in - Java

Question

I am not sure how you are supposed to read in from system input from a Java file   I want to be able to call java myProg  lt  file  Where file is what I want to be read in as a string and given to myProg in the main method   Any suggestions

User · Answer

Use System in  it is an InputStream which just serves this purpose

User · Answer

You probably looking for something like this   FileInputStream in   new FileInputStream  inputFile txt    BufferedReader br   new BufferedReader new InputStreamReader in

User · Answer

You would read from System in just like you would for keyboard input using  for example  InputStreamReader or Scanner

User · Answer

Well  you may read System in itself as it is a valid InputStream  Or also you can wrap it in a BufferedReader    BufferedReader br   new BufferedReader new InputStreamReader System in

User · Answer

You can call java myProg arg1 arg2        public static void main  String args          BufferedReader in   new BufferedReader new FileReader args 0

User · Answer

class myFileReaderThatStarts with arguments     class MissingArgumentException extends Exception              MissingArgumentException String s           super s                 public static void main String   args  throws MissingArgumentException     You can test args array for value  if args length gt 0           do something with args 0    else      default in a path     or     throw new MissingArgumentException  You need to start this program with a path

User · Answer

You can use System in to read from the standard input  It works just like entering it from a keyboard  The OS handles going from file to standard input   class MyProg        public static void main String   args            Scanner sc   new Scanner System in           System out println  Printing the file passed in             while sc hasNextLine    System out println sc nextLine

User · Answer

In Java  console input is accomplished by reading from System in  To obtain a character based stream that is attached to the console  wrap System in in a BufferedReader object  BufferedReader supports a buffered input stream  Its most commonly used constructor is shown here   BufferedReader Reader inputReader    Here  inputReader is the stream that is linked to the instance of BufferedReader that is being created  Reader is an abstract class  One of its concrete subclasses is InputStreamReader  which converts bytes to characters    To obtain an InputStreamReader object that is linked to System in  use the following constructor   InputStreamReader InputStream inputStream    Because System in refers to an object of type InputStream  it can be used for inputStream  Putting it all together  the following line of code creates a BufferedReader that is connected to the keyboard       BufferedReader br   new BufferedReader new InputStreamReader System in      After this statement executes  br is a character-based stream that is linked to the console through System in   This is taken from the book Java- The Complete Reference by Herbert Schildt

[java] Reading in from System.in - Java

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