称之为Scala“;“val函数”;来自Java的错误
我有一个scala val函数,如下所示:称之为Scala“;“val函数”;来自Java的错误,java,scala,scala-java-interop,Java,Scala,Scala Java Interop,我有一个scala val函数,如下所示: val getTimestampEpochMillis = (year:Int, month:Int, day:Int, hour:Int, quarterHour:Int, minute:Int, seconds:Int) => { var tMinutes = minute var tSeconds = seconds if(minute == 0){ if(quarterHour == 1){
val getTimestampEpochMillis = (year:Int, month:Int, day:Int, hour:Int, quarterHour:Int, minute:Int, seconds:Int) => {
var tMinutes = minute
var tSeconds = seconds
if(minute == 0){
if(quarterHour == 1){
tMinutes = 22
tSeconds = 30
}else if(quarterHour == 2){
tMinutes = 37
tSeconds = 30
}else if(quarterHour == 3){
tMinutes = 52
tSeconds = 30
}else if(quarterHour == 0){
tMinutes = 7
tSeconds = 30
}
}
val localDateTime = LocalDateTime.of(year, month, day, hour, tMinutes, tSeconds)
localDateTime.atZone(ZoneId.of("GMT")).toInstant().toEpochMilli()
}
当我从Java调用这个函数时,
我得到以下错误:
[ERROR] required: no arguments
[ERROR] found: int,int,int,int,int,int,int
[ERROR] reason: actual and formal argument lists differ in length
调用scala val函数的Java代码:
Long minTimestampOfGranularity = getTimestampEpochMillis(year, 1, 1, 0, 0, 0, 0);
试一试
请注意gettimestampepepochmillis()
中的括号()
。使用我们得到的
public scala.Function7 getTimestampEpochMillis();
我们看到的
getTimestampEpochMillis()
返回scala.Function7
,因此我们首先必须调用getTimestampEpochMillis()
,然后才能应用这些参数。getTimestampEpochMillis.apply(…)
谢谢。。你能把它作为解释如何、为什么等的答案吗?Java不使用sugar函数语法,将(…)
映射到apply
,因为Scala中的函数是类Function1
,Function2
的实例。。。这些类有一个apply
方法,每当您在Scala中调用这些函数时,就会调用该方法。但是,您必须使用Java显式地调用这些apply
方法。
getTimestampEpochMillis().apply(year, 1, 1, 0, 0, 0, 0);
public scala.Function7<java.lang.Object, java.lang.Object, java.lang.Object, java.lang.Object, java.lang.Object, java.lang.Object, java.lang.Object, scala.runtime.BoxedUnit> getTimestampEpochMillis();