List<Float>转float[] List<Double>转double[]

1. 添加pom

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
</dependency>

 

2. List<Float>转float[] 

List<Float> feature = (List<Float>) jr.get("features");
Float[] ff = feature.toArray(new Float[0]);//这样会报异常：java.lang.ArrayStoreException: null

//需要先转
JSONArray jarr = jr.getJSONArray("features");
Integer s = jarr.size();
List<Float> listF = new ArrayList<Float>();
for(Integer i =0; i<s;i++) {
   listF.add(jarr.getFloat(i));
}
Float[] ffs = listF.toArray(new Float[0]);//0自动匹配大小

float[] floatArray = ArrayUtils.toPrimitive(ffs);

3. List<Double>转double[]

List<Double> yList = new ArrayList<Double>();
Double[] dx = xList.toArray(new Double[xList.size()]);
double[] xArray = (double[]) ArrayUtils.toPrimitive(dx);