在Java中如何使用Lambda表达式实现DoubleToLongFunction？
DoubleToLongFunction是一个内置函数接口java.util.function函数Java8中引入的包。此函数接口接受双值参数并生成长值结果。DoubleToLongFunction接口可用作lambda表达式或方法引用的赋值目标。它只包含一个抽象方法：applyAsLong()。
语法
@FunctionalInterface
public interface DoubleToLongFunction {
long applyAsLong(double value)
}示例
import java.util.function.DoubleToLongFunction;
public class DoubleToLongFunctionTest {
public static void main(String args[]) {
double dbl = 30.1212;
DoubleToLongFunction castToLong = (dblValue) -> (long) dblValue; //lambda表达式
System.out.println(castToLong.applyAsLong(dbl));
dbl = 77.9212;
DoubleToLongFunction roundToLong = Math::round;
System.out.println(roundToLong.applyAsLong(dbl));
}
}输出结果
30 78