问为什么Gradle Build在包含依赖项后仍会失败？

EN

  repositories { mavenCentral() }
    dependencies {
        compile "joda-time:joda-time:2.2"
    }

PS C:\Users\PMath\repositories\gradle> gradle build
:compileJava
C:\Users\PMath\repositories\gradle\src\main\java\hello\HelloWorld.java:3: error: package org.joda.time does not exis
t
import org.joda.time.LocalTime;
                    ^
C:\Users\PMath\repositories\gradle\src\main\java\hello\HelloWorld.java:7: error: cannot find symbol
        LocalTime currentTime = new LocalTime();
        ^
  symbol:   class LocalTime
  location: class HelloWorld
C:\Users\PMath\repositories\gradle\src\main\java\hello\HelloWorld.java:7: error: cannot find symbol
        LocalTime currentTime = new LocalTime();
                                    ^
  symbol:   class LocalTime
  location: class HelloWorld
3 errors
:compileJava FAILED

FAILURE: Build failed with an exception.