我有一段Clojure代码,输出的结果是BigInteger。
(ns com.domain.tiny
(:gen-class
:name com.domain.tiny
:methods [#^{:static true} [binomial [int int] java.math.BigInteger]]))
(defn binomial
"Calculate the binomial coefficient."
[n k]
(let [a (inc n)]
(loop [b 1
c 1]
(if (> b k)
c
(recur (inc b) (* (/ (- a b) b) c))))))
(defn -binomial
"A Java-callable wrapper around the 'binomial' function."
[n k]
(binomial n k))
(defn -main []
(println (str "(binomial 5 3): " (binomial 5 3)))
(println (str "(binomial 10042 111): " (binomial 10042 111)))
)
如果作为独立程序运行,我可以轻松地获得结果:
(binomial 5 3): 10
(binomial 10042 111):
4906838957506814494663377752836616342 ...
48178314846156008309671682804824359157818666487159757179543983405334334410427200
我可以使用lein uberjar
命令生成jar文件。尝试从Java中使用它时,我编写了以下代码。
import com.domain.tiny;
import java.math.BigInteger;
public class Hello
{
public static void main(String[] args) {
BigInteger res = tiny.binomial(5, 3);
System.out.println("(binomial 5 3): " + res);
res = tiny.binomial(10042, 111);
System.out.println("(binomial 10042, 111): " + res);
}
}
很不幸,我遇到了异常。
Exception in thread "main" java.lang.ClassCastException: java.lang.Long cannot be cast
to java.math.BigInteger
at com.domain.tiny.binomial(Unknown Source)
at Hello.main(Hello.java:11)
我该如何在Clojure和Java中进行Java.Math.BigInteger的互操作?我可以使用:methods [#^{:static true} [binomial [int int] double]]))
和 double res = tiny.binomial(10042, 111);
但不适用于BigInteger。
以下是我获取jar包并执行java的步骤:
lein new com.domain.tiny
copy the tiny.clj in com.domain
lein deps
lein uberjar
javac -cp .:com.domain.tiny-1.0.0-SNAPSHOT-standalone.jar Hello.java
java -cp .:com.domain.tiny-1.0.0-SNAPSHOT-standalone.jar Hello
以下clojure代码是从Calling clojure from java复制而来: