When I execute following code in scala REPL console:
java.util.Collections.max(new java.util.ArrayList开发者_如何学JAVA[String]())
NoSuchMethodError exception is thrown:
java.lang.NoSuchMethodError: java.util.Collections.max(Ljava/util/Collection;)Lj
ava/lang/Comparable;
        at .<init>(<console>:8)
        at .<clinit>(<console>)
        at .<init>(<console>:11)
        at .<clinit>(<console>)
        at $export(<console>)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.
java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces
sorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:592)
        at scala.tools.nsc.interpreter.IMain$Request$$anonfun$10.apply(IMain.sca
la:828)
        at scala.tools.nsc.interpreter.Line$$anonfun$1.apply$mcV$sp(Line.scala:4
3)
        at scala.tools.nsc.io.package$$anon$2.run(package.scala:31)
        at java.lang.Thread.run(Thread.java:662)
Scala 2.9.0.1, Java 1.6.0_25
Why an exception is thrown here?
The same code executed from Java behaves as expected (throws NoSuchElementException).
This is a compiler bug that is affecting both Scala 2.8 and 2.9, where the compiler does not compute the proper erasured method signature. I am not aware of a bug report.
Compiling the method:
object Test { def main(a: Array[String]) {
  val a = new java.util.ArrayList[String]()
  java.util.Collections.max(a)
}}
Results into the following bytecode:
public void main(java.lang.String[]);
  Code:
   Stack=2, Locals=3, Args_size=2
   0:   new #16; //class java/util/ArrayList
   3:   dup
   4:   invokespecial   #18; //Method java/util/ArrayList."<init>":()V
   7:   astore_2
   8:   aload_2
   9:   invokestatic    #24; //Method java/util/Collections.max:(Ljava/util/Collection;)Ljava/lang/Comparable;
   12:  pop
   13:  return
Please note that bytecode at offset 9 invokes a static method with a Comparable return type, while the actual Collections.max has Object as the return type:
$ javap -p java.util.Collections | grep max
    public static java.lang.Object max(java.util.Collection);
 
         
                                         
                                         
                                         
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