Groovy array. Which difference between [[],[]].toArray() and [[],[]]*.toArray()

Question

I have prepared data for parametrized unit test in groovy:

@Parameterized.Parameters
static List data() {
    [
            ['20101113', 'DATE',
             '20101114', 'DATE',
             'some statement',
             '20101101T000000/20110101T000000',
             null,
             ['some', 'expected', 'data', 'results']]
    // ...and other 
    ]*.toArray()
}

it works correctly. I checked this code, and tried simplify replacing ]*.toArray() with ].toArray().

java.lang.Exception: FirstParametrizedTest.data() must return a Collection of arrays.

at org.junit.runners.Parameterized$TestClassRunnerForParameters.computeParams(Parameterized.java:94)
at org.junit.runners.Parameterized$TestClassRunnerForParameters.createTest(Parameterized.java:86)
at org.junit.runners.BlockJUnit4ClassRunner$1.runReflectiveCall(BlockJUnit4ClassRunner.java:236)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.BlockJUnit4ClassRunner.methodBlock(BlockJUnit4ClassRunner.java:233)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
at org.junit.runners.Suite.runChild(Suite.java:128)
at org.junit.runners.Suite.runChild(Suite.java:24)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:51)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:237)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

I reverted my change back and it works, but I can't understand why instruction ].toArray() was unexpected? How does ].toArray() work and which difference between ].toArray() and ]*.toArray()?

Groovy array. Which difference between [[],[]].toArray() and [[],[]]*.toArray()

1 Answers