用RMI计算Pi

package client;


import java.rmi.registry.LocateRegistry;/** 来自 nowjava - 时代Java**/

import java.rmi.registry.Registry;

import java.math.BigDecimal;

import compute.Compute;


public class ComputePi {

    public static void main(String args[]) {

        if (System.getSecurityManager() == null) {

            System.setSecurityManager(new SecurityManager());

        }

        try {

            String name = "Compute";

            Registry registry = LocateRegistry.getRegistry(args[0]);

            Compute comp = (Compute) registry.lookup(name);

            Pi task = new Pi(Integer.parseInt(args[1]));

            BigDecimal pi = comp.executeTask(task);

            System.out.println(pi);

        } catch (Exception e) {
        /*
        时代Java公众号 提供
        */

            System.err.println("ComputePi exception:");

            e.printStackTrace();

        }

    }

}


package client;


import compute.Task;

import java.io.Serializable;

import java.math.BigDecimal;


public class Pi implements Task<BigDecimal>, Serializable {


    private static final long serialVersionUID = 227L;


    /** constants used in pi computation */

    private static final BigDecimal FOUR = BigDecimal.valueOf(4);


    /** rounding mode to use during pi computation */

    private static final int roundingMode = BigDecimal.ROUND_HALF_EVEN;


    /** digits of precision after the decimal point */

    private final int digits;


    /**

     * Construct a task to calculate pi to the specified

     * precision.

     */

    public Pi(int digits) {

        this.digits = digits;

    }


    /**

     * Calculate pi.

     */

    public BigDecimal execute() {

        return computePi(digits);

    }


    /**

     * Compute the value of pi to the specified number of 

     * digits after the decimal point.  The value is 

     * computed using Machin's formula:

     *

     *          pi/4 = 4*arctan(1/5) - arctan(1/239)

     *

     * and a power series expansion of arctan(x) to 

     * sufficient precision.

     */

    public static BigDecimal computePi(int digits) {

        int scale = digits + 5;

        BigDecimal arctan1_5 = arctan(5, scale);

        BigDecimal arctan1_239 = arctan(239, scale);

        BigDecimal pi = arctan1_5.multiply(FOUR).subtract(arctan1_239)

                .multiply(FOUR);

        return pi.setScale(digits, BigDecimal.ROUND_HALF_UP);

    }


    /**

     * Compute the value, in radians, of the arctangent of 

     * the inverse of the supplied integer to the specified

     * number of digits after the decimal point.  The value

     * is computed using the power series expansion for the

     * arc tangent:

     *

     * arctan(x) = x - (x^3)/3 + (x^5)/5 - (x^7)/7 + 

     *     (x^9)/9 ...

     */

    public static BigDecimal arctan(int inverseX, int scale) {

        BigDecimal result, numer, term;

        BigDecimal invX = BigDecimal.valueOf(inverseX);

        BigDecimal invX2 = BigDecimal.valueOf(inverseX * inverseX);


        numer = BigDecimal.ONE.divide(invX, scale, roundingMode);


        result = numer;

        int i = 1;

        do {

            numer = numer.divide(invX2, scale, roundingMode);

            int denom = 2 * i + 1;

            term = numer.divide(BigDecimal.valueOf(denom), scale,

                    roundingMode);

            if ((i % 2) != 0) {

                result = result.subtract(term);

            } else {

                result = result.add(term);

            }

            i++;

        } while (term.compareTo(BigDecimal.ZERO) != 0);

        return result;

    }

}


---

HTML

<p>Compute.java</p>



---

Code


package compute;


import java.rmi.Remote;

import java.rmi.RemoteException;


public interface Compute extends Remote {

    <T> T executeTask(Task<T> t) throws RemoteException;

}

---

HTML

<p>Task.java</p>



---

Code


package compute;


public interface Task<T> {

    T execute();

}


/*

 * Copyright (c) 1995, 2008, Oracle and/or its affiliates. All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 *   - Redistributions of source code must retain the above copyright

 *     notice, this list of conditions and the following disclaimer.

 *

 *   - 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.

 *

 *   - Neither the name of Oracle or the names of its

 *     contributors may be used to endorse or promote products derived

 *     from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.

 */

---

HTML

<p>ComputeEngine.java</p>



---

Code


package engine;


import java.rmi.RemoteException;

import java.rmi.registry.LocateRegistry;

import java.rmi.registry.Registry;

import java.rmi.server.UnicastRemoteObject;

import compute.Compute;

import compute.Task;


public class ComputeEngine implements Compute {


    public ComputeEngine() {

        super();

    }


    public <T> T executeTask(Task<T> t) {

        return t.execute();

    }


    public static void main(String[] args) {

        if (System.getSecurityManager() == null) {

            System.setSecurityManager(new SecurityManager());

        }

        try {

            String name = "Compute";

            Compute engine = new ComputeEngine();

            Compute stub = (Compute) UnicastRemoteObject.exportObject(

                    engine, 0);

            Registry registry = LocateRegistry.getRegistry();

            registry.rebind(name, stub);

            System.out.println("ComputeEngine bound");

        } catch (Exception e) {

            System.err.println(