交換兩個可變由Scala語言

Question

val numClasses = 5 
val categoricalFeaturesInfo = Map[Int, Int]() 
val impurity = "gini" 
val maxDepth = 0 
val maxBins = 32 
val greaccuracy = 0 
for(maxDepth <- 0 to 30){ 
val model = DecisionTree.trainClassifier(trainData, numClasses, categoricalFeaturesInfo, impurity, maxDepth, maxBins) 
val metrics = getMetrics(model, cvData) 
val accuracy = metrics.precision 
if (accuracy > greaccuracy){ 
greaccuracy = accuracy 
} 
} 
println("Accuracy = "+greaccuracy) 

請任何幫助 錯誤：重新分配給VAL greaccuracy =準確性 ^

Answer 1

VAL是不可改變的變量，一旦設置你不能改變它們。這是由設計。另一方面，你可以改變它們。