testResult.out

======= expection results for 10 elements, and every values are 1 =======
======= test for 1000 times =========
Exception in thread "Thread-4" java.lang.ArrayIndexOutOfBoundsException: 1
	at java.util.ArrayList.add(ArrayList.java:459)
	at java_util_List$add.call(Unknown Source)
	at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125)
	at ThreadSafeTest$_parallelExecute_closure1$_closure6.doCall(ThreadSafeTest.groovy:6)
	at ThreadSafeTest$_parallelExecute_closure1$_closure6.doCall(ThreadSafeTest.groovy)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
	at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
	at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:294)
	at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1024)
	at groovy.lang.Closure.call(Closure.java:414)
	at groovy.lang.Closure.call(Closure.java:408)
	at groovy.lang.Closure.run(Closure.java:495)
	at java.lang.Thread.run(Thread.java:745)
====== error =====
results: [null, null, 1, 1, 1, 1, 1, 1, 1, 1], size: 10
====== error =====
happened at 0
====== error =====
results: [1, 1, 1, 1, null, 1, 1, 1, 1, 1], size: 10
====== error =====
happened at 375
====== error =====
results: [1, 1, 1, 1, null, 1, 1, 1, 1, 1], size: 10
====== error =====
happened at 490
====== error =====
results: [1, 1, 1, 1, 1, 1, null, 1, 1, 1], size: 10
====== error =====
happened at 805
======= success: 996 / 1000

ThreadNotSafeTest.groovy

def parallelExecute(List<Closure> executions) {
    def results = []
    def threads = []
    executions.collect { execution ->
        def th = new Thread({
            results.add(execution())
        })
        threads.add(th)
    }
    threads.each { it.start() }
    threads.each { it.join()  }
    results
}
def singleTest(listValue, execNum) {
    def execs = []
    for(int i  =0; i<execNum; i++) {
        execs.add({ -> listValue})
    }
    def results = parallelExecute(execs);
    def size = results.size
    if( !size == execNum || !results.every { elm -> elm == listValue}) {
        println "====== error ====="
        println "results: $results, size: $size"
        println "====== error ====="
        return false
    } else {
        return true
    }
}
println "======= expection results for 10 elements, and every values are 1 ======="
def testNum = 1000
println "======= test for $testNum times ========="
def success = 0
for(int i = 0; i < testNum; i++) {
    if(!singleTest(1, 10)) {
        println "happened at $i"
    } else {
        success++
    }
}
println "======= success: $success / $testNum"

ThreadSafeFix.groovy

def parallelExecute(List<Closure> executions) {
    def results = []
    def threads = []
    executions.collect { execution ->
        def resultContainer = []
        results.add(resultContainer)
        def th = new Thread({
            resultContainer.add(execution())
        })
        threads.add(th)
    }
    threads.each { it.start() }
    threads.each { it.join()  }
    results.collect { resultContainer -> resultContainer[0] }
}