CSC212 Lab 5 Solutions 2014

--D. Thiebaut (talk) 07:26, 28 September 2014 (EDT)

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Lab5Bomb.java

import java.util.Scanner;

public class Lab5Bomb {
	
	public static void main(String[] args) {
		Scanner input = new Scanner( System.in );
		
		while ( true ) {
			System.out.println( "Please enter 2 integers (-1 to stop): ");
			int n1, n2;
			try {
				n1 = input.nextInt();
				if ( n1==-1 ) break;
				n2 = input.nextInt();
			} catch ( InputMismatchException e ) {
				System.out.println( "You must enter an integer.  Please reenter." );
				input.nextLine();
				continue;
			}
			
			
			try {
				System.out.println( n1 + " / " + n2 + " is " + (n1/n2) );
			}
			catch ( ArithmeticException e ) {
				System.out.println( "Exception: " + e.getMessage() + 
									"\nReenter numbers." );
			}
		}

	}

}

Lab5ReadFile.java

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;


public class Lab5ReadFile {
    public static void main( String[] args ) {
        
      String fileName;
      int n1, n2;
      Scanner inFile = null;
      
      if ( args.length  == 0 ) {
          System.out.println( "Syntax: java Lab5ReadFile textFileName" );
          System.out.println( "        where textFileName is a name of a data file.");
          return;
      }
      
      fileName = args[0];
      
      try { 
          inFile = new Scanner( new File( fileName ) );
      } catch ( FileNotFoundException e ) { 
          System.out.println( "File does not exist.");
          return;
      }
      
      while ( inFile.hasNext() ) {
          n1 = inFile.nextInt();
          n2 = inFile.nextInt();
          System.out.println( n1 + " / " + n2 + " is " + n1/n2 );
      }
    }
}

Lab5ReadFileThrow2.java

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class Lab5ReadFileThrow2 {

	private static Scanner openFile( String fileName ) throws FileNotFoundException {
		Scanner inFile;
		inFile = new Scanner(new File(fileName));
		return inFile;
	}
	
	private static int[] get2Ints( Scanner inFile ) {
		int n1 = inFile.nextInt(); 
		int n2 = inFile.nextInt();
		return new int[] { n1, n2 };
	}
	
	public static void main(String[] args) {
		
		Scanner inFile = null;

		// if user forgot the enter file name on command line, remind her
		if (args.length == 0) {
			System.out.println("Syntax: java Lab5ReadFile textFileName");
			System.out
					.println("        where textFileName is a name of a data file.");
			return;
		}

		// set file name to first argument on command line
		try {
			inFile = openFile( args[0] );
		} catch (FileNotFoundException e) {
			System.err.println( "Could not find file " + args[0] );
			return;
		}

		// read the file
		while (inFile.hasNext()) {
			int[] a = get2Ints( inFile );
			System.out.println( a[0] + " / " + a[1] + " is " + a[0] / a[1] );
		}
	}
}

Lab5ReadFileThrow3.java

import java.io.File;
import java.io.FileNotFoundException;
import java.util.InputMismatchException;
import java.util.Scanner;

class MyException extends Exception {
  MyException( String  message ) {
      super( message );
  }
}

public class Lab5ReadFileThrow3 {

  private static Scanner openFile( String fileName ) 
                                 throws FileNotFoundException {
      Scanner inFile;
      inFile = new Scanner(new File(fileName));
      return inFile;
  }
    
    private static int[] get2Ints( Scanner inFile ) 
                      throws InputMismatchException, MyException {
        int n1 = inFile.nextInt(); 
        int n2 = inFile.nextInt();
        if ( n2 == 0 ) 
            throw new MyException( "Invalid 2nd operand: 0\n" );
        return new int[] { n1, n2 };
    }
    
    public static void main(String[] args) {
        
        Scanner inFile = null;
        
        // if user forgot the enter file name 
        // on command line, remind her
        if (args.length == 0) {
            System.out.println("Syntax: java Lab5ReadFile"
                               + " textFileName");
            System.out.println("        where textFileName "
                               + "is a name of a data file.");
            return;
        }
        
        // set file name to first argument on command line
        try {
            inFile = openFile( args[0] );
        } catch (FileNotFoundException e) {
            System.err.println( "Could not find file " + args[0] );
            return;
        }
        
        // read the file
        while (inFile.hasNext()) {
            int[] a;
            try {
                a = get2Ints( inFile );
            } catch ( InputMismatchException e ) {
                System.out.println( "Wrong number format."+
                                    "Please reenter!" );
                inFile.nextLine();
                continue;
            } catch ( MyException e)  {
                System.out.println( "Invalid second int:"
                                    + "0.  Skipping this line." );
                //inFile.nextLine();
                continue;
            }
            System.out.println( a[0] + " / " + a[1] + " is " + a[0] / a[1] );
        }
    }
}

Lab5ReadFileThrow.java

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class Lab5ReadFileThrow {

	private static Scanner openFile( String fileName ) throws FileNotFoundException {
		Scanner inFile;
		inFile = new Scanner(new File(fileName));
		return inFile;
	}
	
	public static void main(String[] args) {
		int n1, n2;
		Scanner inFile = null;

		// if user forgot the enter file name on command line, remind her
		if (args.length == 0) {
			System.out.println("Syntax: java Lab5ReadFile textFileName");
			System.out
					.println("        where textFileName is a name of a data file.");
			return;
		}

		// set file name to first argument on command line
		try {
			inFile = openFile( args[0] );
		} catch (FileNotFoundException e) {
			System.err.println( "Could not find file " + args[0] );
			return;
		}

		// read the file
		while (inFile.hasNext()) {
			n1 = inFile.nextInt();
			n2 = inFile.nextInt();
			System.out.println(n1 + " / " + n2 + " is " + n1 / n2);
		}
	}
}