当你需要存储(非常)大数字时该怎么办?

我试图做一个项目欧拉问题,但它涉及添加一个非常大的数字的数字。 (100!)

使用Java int和long太小了。

谢谢你的任何建议

类BigInteger看起来可能就是你想要的。

使用BigInteger 。 以下是一本关于通过缓存计算因子计算的“坚果壳中的Java示例”一书中的示例

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 "); } // 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)); } } 

java.lang.BigInteger或java.lang.BigDecimal

 import java.math.BigInteger; import java.util.*; public class Main { protected static ArrayList table = new ArrayList(); 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)); } }