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This program was compiled with the command javac InputLibrary.java on a system with Java 1.5.0. When run from the command line with java InputLibrary, the program will successfully take two characters as input and print them out. However, when run with java InputLibrary < input, where input is a file that contains the exact same input, the program throws an IOException prints "ERROR" because the second call to getChar() finds no characters to read.

Code Block

bgColor	#FFCCCC

import java.io.BufferedInputStream;
import java.io.IOExceptionEOFException;

public final class InputLibrary{

  public static char getChar()throws IOExceptionEOFException {
    BufferedInputStream in = new BufferedInputStream(System.in);
    int input = in.read();
    if(input==-1){
    	throw new IOException("Premature end of input."EOFException();
    }
    return (char)input; //okay because InputStream guarantees read() will fit in a byte if it is not -1
  }

  public static void main(String[] args)throws{
   IOException try{
      System.out.print("Enter first initial: ");
      char first=getChar();
      System.out.println("Your first initial is "+first);
      System.out.print("Enter last initial: ");
      char last=getChar();
      System.out.println("Your last initial is "+last);
    }catch(EOFException e){
      System.out.println("ERROR");
    }
  }
}

Compliant Solution

Create and use only a single BufferedInputStream on System.in. This code example stores the BufferedInputStream as a class variable so all methods can access it. However, if a program were to use this library in conjunction with other input from a user that also needs some buffered wrapper on System.in, the library would need to be modified so that all code uses the same buffered wrapper instead of creating separate ones.

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Code Block

bgColor	#ccccff

import java.io.BufferedInputStream;
import java.io.IOExceptionEOFException;

public final class InputLibrary{

  private static BufferedInputStream in = new BufferedInputStream(System.in);

  public static char getChar()throws IOExceptionEOFException {
    int input = in.read();
    if(input==-1){
    	throw new IOException("Premature end of input."EOFException();
    }
    in.skip(1); //This linestatement now necessary to go to the next line
                //inthe theNoncompliant previouscode example code deceptively worked without it
    return (char)input; //okay because InputStream guarantees read() will fit in a byte if it is not -1
  }

  public static void main(String[] args)throws{
   IOException try{
      System.out.print("Enter first initial: ");
      char first=getChar();
      System.out.println("Your first initial is "+first);
      System.out.print("Enter last initial: ");
      char last=getChar();
      System.out.println("Your last initial is "+last);
    }catch(EOFException e){
      System.out.println("ERROR");
    }
  }
}

Risk Assessment

Creating multiple buffered wrappers on an InputStream can crash the cause unexpected program behavior when the InputStream is re-directed.

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Versions Compared

Old Version 15

New Version 16

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Compliant Solution

Risk Assessment