我编写了一个类,使用Apache数学(不管),我有一个奇怪的故障(或者也许有我的Java代码中的问题?)。Clojure:java interop,为什么这段代码不起作用?
这里是代码
package distributions;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
import org.apache.commons.math3.distribution.AbstractIntegerDistribution;
import org.apache.commons.math3.util.FastMath;
public class CustomDistribution extends AbstractIntegerDistribution {
long[] v;
double[] p;
double[] cp;
Map<Long, Double> mp = new HashMap<Long, Double>();
Map<Long, Double> mcp = new HashMap<Long, Double>();
public CustomDistribution (long[] values, double[] probabilities) {
v = values;
p = probabilities;
int len = values.length;
for (int i = 0; i < len; i++) {
mp.put(v[i], p[i]);
}
cp = new double[len];
cp[0] = p[0];
for (int i = 1; i < len; i++) {
cp[i] = cp[i-1] + p[i];
}
for (int i = 0; i < len; i++) {
mcp.put(v[i], cp[i]);
}
}
public Map<Long, Double> getMCP() {return mcp;}
@Override
public double cumulativeProbability(int v) {
return mcp.get(v);
}
// Not implemented, can be done in Clojure code
@Override
public double getNumericalMean() {
return 0;
}
// Not implemented, can be done in Clojure code
@Override
public double getNumericalVariance() {
return 0;
}
@Override
public int getSupportLowerBound() {
return 0;
}
@Override
public int getSupportUpperBound() {
return 0;
}
@Override
public boolean isSupportConnected() {
return false;
}
@Override
public double probability(int v) {
return mp.get(v);
}
// Uses a naive search implementation, should be ok due to data size
public int sample() {
double r = FastMath.random();
int len = p.length;
Boolean flag = false;
int i = 0;
int result = -1;
while (i < len && flag == false) {
if (cp[i] < r) {
i = i + 1;
}
else {
result = (int) v[i];
flag = true;
}
}
return result;
}
}
Clojure的包装:
(defn create-distribution
"Creates a distribution from empirical data"
[data]
(let [values (long-array (data :values))
probabilities (double-array (data :probabilities))]
(CustomDistribution. values probabilities)))
(create-distribution {:values [1 2 3 4] :probabilities [0.3 0.2 0.2 0.3]})
基本上它是内部有两种形式的数据分布:包含HashMap和阵列。
在Clojure中,我想:
(.probability dist 4)
(.probability dist (int 4))
两个回报NullPointerException异常,NativeMethodAccessorImpl..blabla 相同的.cumulativeProbabilityMethod (在另一方面,所以它可能是HashMap中的一个问题。样品工作正常)
我想通了,也许在构造函数中MCP和MP(即是包含HashMap)没有正确的构造函数计算的,但是当我尝试:
(.get (.getMCP dist) 4)
它返回我正确的结果。实际上,MCP hashmap是我预期的结果。
那么为什么我的代码不起作用?我的两条线在功能上是一样的。 如果我犯了一个错字,我没有看到它。 也许是因为不变性的原因?
谢谢!