SimpleCalcScanner.java Source code

Introduction

Here is the source code for SimpleCalcScanner.java

Source

/*
* Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* 
* Java, the Duke mascot, and all variants of Sun's Java "steaming coffee
* cup" logo are trademarks of Sun Microsystems. Sun's, and James Gosling's,
* pioneering role in inventing and promulgating (and standardizing) the Java 
* language and environment is gratefully acknowledged.
* 
* The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
* inventing predecessor languages C and C++ is also gratefully acknowledged.
*/

import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.Reader;
import java.util.Scanner;
import java.util.Stack;

/**
* SimpleCalc -- simple calculator using 1.5 java.util.Scanner
* @version   $Id: SimpleCalcScanner.java,v 1.3 2004/03/10 18:01:35 ian Exp $
*/
public class SimpleCalcScanner {
    /** The Scanner */
    protected Scanner scan;

    /** The output */
    protected PrintWriter out = new PrintWriter(System.out);

    /** The variable name (not used in this version) */
    protected String variable;

    /** The operand stack */
    protected Stack s = new Stack();

    /* Driver - main program */
    public static void main(String[] av) throws IOException {
        if (av.length == 0)
            new SimpleCalcScanner(new InputStreamReader(System.in)).doCalc();
        else
            for (int i = 0; i < av.length; i++)
                new SimpleCalcScanner(av[i]).doCalc();
    }

    /** Construct a SimpleCalcScanner by name */
    public SimpleCalcScanner(String fileName) throws IOException {
        this(new FileReader(fileName));
    }

    /** Construct a SimpleCalcScanner from an open Reader */
    public SimpleCalcScanner(Reader rdr) throws IOException {
        scan = new Scanner(rdr);
        // Control the input character set:
        scan.slashSlashComments(true); // treat "//" as comments
        scan.ordinaryChar('-'); // used for subtraction
        scan.ordinaryChar('/'); // used for division
    }

    /** Construct a SimpleCalcScanner from a Reader and a PrintWriter */
    public SimpleCalcScanner(Reader rdr, PrintWriter pw) throws IOException {
        this(rdr);
        setWriter(pw);
    }

    /** Change the output to go to a new PrintWriter */
    public void setWriter(PrintWriter pw) {
        out = pw;
    }

    protected void doCalc() throws IOException {
        int iType;
        double tmp;

        while (scan.hasNext()) {
            if (scan.hasNextDouble()) {
                push(scan.nextDouble());
            } else {
                String token = scan.next().toString();
                if (token.equals("+")) {
                    // Found + operator, perform it immediately.
                    push(pop() + pop());
                } else if (token.equals("-")) {
                    // Found - operator, perform it (order matters).
                    tmp = pop();
                    push(pop() - tmp);
                } else if (token.equals("*")) {
                    // Multiply is commutative
                    push(pop() * pop());
                } else if (token.equals("/")) {
                    // Handle division carefully: order matters!
                    tmp = pop();
                    push(pop() / tmp);
                } else if (token.equals("=")) {
                    out.println(peek());
                } else {
                    out.println("What's this? " + token);
                }
            }
        }
    }

    void push(double val) {
        s.push(new Double(val));
    }

    double pop() {
        return ((Double) s.pop()).doubleValue();
    }

    double peek() {
        return ((Double) s.peek()).doubleValue();
    }

    void clearStack() {
        s.removeAllElements();
    }
}