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  1. JDK
  2. JDK-8044737

Lambda: NPE while obtaining method reference through lambda expression

    Details

    • Subcomponent:
    • Resolved In Build:
      b22
    • Verification:
      Verified

      Backports

        Description

        Code:

        $ cat Test.java

        public class Test {

            interface Constructor {
                MyTest execute();
            }

            class MyTest {
                MyTest() { System.out.println("Constructor executed"); }
            }

            public Constructor getConstructor() {
                return getConstructor(() -> { return MyTest::new; });
            }

            public static void main(String argv[]) {
                Test t = new Test();
                MyTest mytest = t.getConstructor().execute();
            }

            Constructor getConstructor(Wrapper arg) {
                return arg.unwrap();
            }

            interface Wrapper {
                Constructor unwrap();
            }
        }

        Generates NullPointerException on compilation:

        $ javac Test.java
        An exception has occurred in the compiler (1.9.0-internal). Please file a bug at the Java Developer Connection (http://java.sun.com/webapps/bugreport) after checking the Bug Parade for duplicates. Include your program and the following diagnostic in your report. Thank you.
        java.lang.NullPointerException
        at com.sun.tools.javac.jvm.Code.emitop0(Code.java:563)
        at com.sun.tools.javac.jvm.Items$SelfItem.load(Items.java:367)
        at com.sun.tools.javac.jvm.Gen.genArgs(Gen.java:959)
        at com.sun.tools.javac.jvm.Gen.visitApply(Gen.java:1898)
        at com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1459)
        at com.sun.tools.javac.jvm.Gen.genExpr(Gen.java:940)
        at com.sun.tools.javac.jvm.Gen.visitReturn(Gen.java:1856)
        at com.sun.tools.javac.tree.JCTree$JCReturn.accept(JCTree.java:1378)
        at com.sun.tools.javac.jvm.Gen.genDef(Gen.java:730)
        at com.sun.tools.javac.jvm.Gen.genStat(Gen.java:765)
        at com.sun.tools.javac.jvm.Gen.genStat(Gen.java:751)
        at com.sun.tools.javac.jvm.Gen.genStats(Gen.java:802)
        at com.sun.tools.javac.jvm.Gen.visitBlock(Gen.java:1151)
        at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:903)
        at com.sun.tools.javac.jvm.Gen.genDef(Gen.java:730)
        at com.sun.tools.javac.jvm.Gen.genStat(Gen.java:765)
        at com.sun.tools.javac.jvm.Gen.genMethod(Gen.java:1024)
        at com.sun.tools.javac.jvm.Gen.visitMethodDef(Gen.java:987)
        at com.sun.tools.javac.tree.JCTree$JCMethodDecl.accept(JCTree.java:772)
        at com.sun.tools.javac.jvm.Gen.genDef(Gen.java:730)
        at com.sun.tools.javac.jvm.Gen.genClass(Gen.java:2518)
        at com.sun.tools.javac.main.JavaCompiler.genCode(JavaCompiler.java:744)
        at com.sun.tools.javac.main.JavaCompiler.generate(JavaCompiler.java:1571)
        at com.sun.tools.javac.main.JavaCompiler.generate(JavaCompiler.java:1535)
        at com.sun.tools.javac.main.JavaCompiler.compile2(JavaCompiler.java:906)
        at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:865)
        at com.sun.tools.javac.main.Main.compile(Main.java:521)
        at com.sun.tools.javac.main.Main.compile(Main.java:381)
        at com.sun.tools.javac.main.Main.compile(Main.java:370)
        at com.sun.tools.javac.main.Main.compile(Main.java:361)
        at com.sun.tools.javac.Main.compile(Main.java:56)
        at com.sun.tools.javac.Main.main(Main.java:42)

        Changing 'getConstructor()' method to implementation without lambda wrapper works good:

            public Constructor getConstructor() {
                return MyTest::new;
            }

        $ javac Test.java
        $ java Test
        Constructor executed

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                • Assignee:
                  rfield Robert Field
                  Reporter:
                  spikalev Sergei Pikalev (Inactive)
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                  Dates

                  • Created:
                    Updated:
                    Resolved: