Fel是支持表达式计算的一个库(java)。
Fel支持解释执行和编译执行，可以根据性能要求选择执行方式。
下面给出示例和性能测试数据：
package datagene;
import java.util.Random;
import com.greenpineyu.fel.Expression;
import com.greenpineyu.fel.FelEngine;
import com.greenpineyu.fel.FelEngineImpl;
import com.greenpineyu.fel.context.FelContext;
import com.greenpineyu.fel.parser.FelNode;
public class Expr {
public static void main(String[] args) {
Random random = new Random();
Object result = null;
long time = System.nanoTime();
for(int i = 0; i < ; i++) {
result = random.nextInt(1000) * random.nextInt(1000) +
random.nextInt(1000);
}
System.out.println(((float)(System.nanoTime() – time) / ) + “ms”);
FelEngine fel1 = new FelEngineImpl();
FelContext ctx1 = fel1.getContext();
time = System.nanoTime();
for(int i = 0; i < ; i++) {
ctx1.set(“a”, random.nextInt(1000));
ctx1.set(“b”, random.nextInt(1000));
ctx1.set(“c”, random.nextInt(1000));
result = fel1.eval(“a * b + c”);
}
System.out.println(((float)(System.nanoTime() – time) / ) + “ms”);
FelEngine fel2 = new FelEngineImpl();
FelNode node = fel2.parse(“a * b + c”);
FelContext ctx2 = fel2.getContext();
time = System.nanoTime();
for(int i = 0; i < ; i++) {
ctx2.set(“a”, random.nextInt(1000));
ctx2.set(“b”, random.nextInt(1000));
ctx2.set(“c”, random.nextInt(1000));
result = node.eval(ctx2);
}
System.out.println(((float)(System.nanoTime() – time) / ) + “ms”);
FelEngine fel3 = new FelEngineImpl();
Expression exp = fel3.parse(“a * b + c”);
FelContext ctx3 = fel3.getContext();
time = System.nanoTime();
for(int i = 0; i < ; i++) {
ctx3.set(“a”, random.nextInt(1000));
ctx3.set(“b”, random.nextInt(1000));
ctx3.set(“c”, random.nextInt(1000));
result = exp.eval(ctx3);
}
System.out.println(((float)(System.nanoTime() – time) / ) + “ms”);
}
}
输出：
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