build failed on Intellij IDEA 2018 with java 8 on windows 10

[tuhaolam]

java version "1.8.0_171"
Java(TM) SE Runtime Environment (build 1.8.0_171-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.171-b11, mixed mode)

Information:java: Errors occurred while compiling module 'flink-training-exercises'
Information:javac 1.8.0_171 was used to compile java sources
Information:2018/9/4 14:35 - Compilation completed with 15 errors and 0 warnings in 10 s 522 ms
D:\java\flink-training-exercises\src\test\java\com\dataartisans\flinktraining\exercises\datastream_java\basics\RideCleansingScalaTest.java
Error:(19, 72) java: package com.dataartisans.flinktraining.exercises.datastream_scala.basics not exists
Error:(27, 112) java: package com.dataartisans.flinktraining.solutions.datastream_scala.basics not exists
D:\java\flink-training-exercises\src\test\java\com\dataartisans\flinktraining\exercises\datastream_java\windows\HourlyTipsScalaTest.java
Error:(19, 73) java: package com.dataartisans.flinktraining.exercises.datastream_scala.windows not exists
Error:(31, 113) java: package com.dataartisans.flinktraining.solutions.datastream_scala.windows not exists
D:\java\flink-training-exercises\src\test\java\com\dataartisans\flinktraining\exercises\datastream_java\process\ExpiringStateScalaTest.java
Error:(19, 73) java: package com.dataartisans.flinktraining.exercises.datastream_scala.process not exists
Error:(27, 113) java: package com.dataartisans.flinktraining.solutions.datastream_scala.process not exists
D:\java\flink-training-exercises\src\test\java\com\dataartisans\flinktraining\exercises\datastream_java\state\RidesAndFaresScalaTest.java
Error:(21, 71) java: package com.dataartisans.flinktraining.exercises.datastream_scala.state not exists
Error:(32, 111) java: package com.dataartisans.flinktraining.solutions.datastream_scala.state not exists
D:\java\flink-training-exercises\src\test\java\com\dataartisans\flinktraining\exercises\datastream_java\windows\PopularPlacesScalaTest.java
Error:(19, 73) java: package com.dataartisans.flinktraining.exercises.datastream_scala.windows not exists
Error:(30, 113) java: package com.dataartisans.flinktraining.solutions.datastream_scala.windows not exists
D:\java\flink-training-exercises\src\test\java\com\dataartisans\flinktraining\exercises\datastream_java\process\LongRidesScalaTest.java
Error:(26, 112) java: package com.dataartisans.flinktraining.exercises.datastream_scala.process not exists
Error:(27, 111) java: package com.dataartisans.flinktraining.exercises.datastream_scala.cep not exists
Error:(30, 113) java: package com.dataartisans.flinktraining.solutions.datastream_scala.process not exists
Error:(35, 112) java: package com.dataartisans.flinktraining.solutions.datastream_scala.cep not exists
Error:(40, 125) java: package com.dataartisans.flinktraining.solutions.datastream_scala.process not exists
D:\java\flink-training-exercises\src\test\java\com\dataartisans\flinktraining\exercises\datastream_java\testing\TestSource.java
Information:java: 某些输入文件使用了未经检查或不安全的操作。
Information:java: 有关详细信息, 请使用 -Xlint:unchecked 重新编译。

[alpinegizmo]

You need to somehow add a scala SDK. You can, for example, do this by opening the project structure dialog to add a Scala 2.11 SDK in the Global Libraries section.