var x= 10if(x>=0){ scala.math.sqrt(x)}else{ throw new IllegalArgumentException("the value should not be negative")}if else表达式的值为res1: Double = 3.1622776601683795
scala中的if else为表达式，表达式就会有值
原文：http://www.cnblogs.com/liuye-micky/p/6910622.html
