ماذا تفعل عندما تحتاج إلى تخزين (جدا) عدد كبير؟

Question

وأنا أحاول القيام به مشكلة في مشروع أويلر ولكنه ينطوي إضافة أرقام من عدد كبير جدا. (100)!

وعن طريق الباحث جافا وطويلة صغيرة جدا.

وشكرا على اي اقتراحات

Answer 1

BigInteger يبدو وكأنها قد يكون ما كنت تبحث عنه.

Answer 2

استخدم BigInteger . هنا هو سبيل المثال من كتاب <م> أمثلة جافا في باختصار ينطوي على عاملي الحوسبة، مع التخزين المؤقت.

import java.math.BigInteger;
import java.util.ArrayList;

/*
 * Copyright (c) 2000 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 2nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or 
 * implied. You may study, use, and modify it for any non-commercial 
 * purpose. You may distribute it non-commercially as long as you 
 * retain this notice. For a commercial use license, or to purchase 
 * the book (recommended), visit 
 * http://www.davidflanagan.com/javaexamples2.
 */

/**
 * This program computes and displays the factorial of a number 
 * specified on the command line. It handles possible user input 
 * errors with try/catch.
 */
public class FactComputer {
  public static void main(String[] args) {
    // Try to compute a factorial.
    // If something goes wrong, handle it in the catch clause below.
    try {
      int x = Integer.parseInt(args[0]);
      System.out.println(x + "! = " + Factorial4.factorial(x));
    }
    // The user forgot to specify an argument.
    // Thrown if args[0] is undefined.
    catch (ArrayIndexOutOfBoundsException e) {
      System.out.println("You must specify an argument");
      System.out.println("Usage: java FactComputer <number>");
    }
    // The argument is not a number. Thrown by Integer.parseInt().
    catch (NumberFormatException e) {
      System.out.println("The argument you specify must be an integer");
    }
    // The argument is < 0. Thrown by Factorial4.factorial()
    catch (IllegalArgumentException e) {
      // Display the message sent by the factorial() method:
      System.out.println("Bad argument: " + e.getMessage());
    }
  }
}

/**
 * This version of the program uses arbitrary precision integers, so it 
 * does not have an upper-bound on the values it can compute. It uses an 
 * ArrayList object to cache computed values instead of a fixed-size 
 * array. An ArrayList is like an array, but can grow to any size. The 
 * factorial() method is declared "synchronized" so that it can be safely 
 * used in multi-threaded programs. Look up java.math.BigInteger and
 * java.util.ArrayList while studying this class.
 * Prior to Java 1.2, use Vector instead of ArrayList
 */

class Factorial4 {
  protected static ArrayList table = new ArrayList(); // create cache
  static { // Initialize the first element of the cache with !0 = 1.
    table.add(BigInteger.valueOf(1));
  }

  /** The factorial() method, using BigIntegers cached in a ArrayList */
  public static synchronized BigInteger factorial(int x) {
    if (x < 0)
      throw new IllegalArgumentException("x must be non-negative.");
    for (int size = table.size(); size <= x; size++) {
      BigInteger lastfact = (BigInteger) table.get(size - 1);
      BigInteger nextfact = lastfact.multiply(BigInteger.valueOf(size));
      table.add(nextfact);
    }
    return (BigInteger) table.get(x);
  }

  /**
   * A simple main() method that we can use as a standalone test 
   * program for our factorial() method.
   */
  public static void main(String[] args) {
    for (int i = 0; i <= 50; i++)
      System.out.println(i + "! = " + factorial(i));
  }
}

Answer 3

وjava.lang.BigInteger أو java.lang.BigDecimal

Answer 4

import java.math.BigInteger;
import java.util.*;

public class Main {
    protected static ArrayList<BigInteger> table = new ArrayList<BigInteger>();

    static {
        table.add(BigInteger.valueOf(1));
    }

    public static synchronized BigInteger factorial(int x) {
        if (x < 0) throw new IllegalArgumentException("x must be non-negative.");
        for (int size = table.size(); size <= x; size++) {
            BigInteger lastfact = table.get(size - 1);
            BigInteger nextfact = lastfact.multiply(BigInteger.valueOf(size));
            table.add(nextfact);
        }
        return table.get(x);
    }

    public static void main(String[] args) {
        for (int i = 0; i <= 50; i++)
            System.out.println(i + "! = " + factorial(i));
    }
}