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  1. JDK
  2. JDK-4119776

illegal 'case' constant expressions

    Details

    • Subcomponent:
    • CPU:
      generic, sparc
    • OS:
      solaris_2.5.1

      Description



      Name: laC46010 Date: 03/16/98


      javac (JDK1.0.2 and later) treats expressions a.b.c and a.c (
      where 'a' names an instance of class T,
      b - non-final reference to T,
      c - final non-static field of class T)
      as a constant expressions which contradicts the JLS (15.27).
      The JLS (15.27) says :
      "A compile-time constant expression is an expression denoting a value
      of primitive type or a String that is composed using only the
      following:

           Literals of primitive type and literals of type String
           Casts to primitive types and casts to type String
           The unary operators +, -, ~, and ! (but not ++ or --)
           The multiplicative operators *, /, and %
           The additive operators + and -
           The shift operators <<, >>, and >>>
           The relational operators <, <=, >, and >= (but not instanceof)
           The equality operators == and !=
           The bitwise and logical operators &, ^, and |
           The conditional-and operator && and the conditional-or operator ||
           The ternary conditional operator ? :
           Simple names that refer to final variables whose initializers are
           constant expressions
           Qualified names of the form TypeName . Identifier that refer to
           final variables whose initializers are constant expressions

      Compile-time constant expressions are used in case labels in switch
      statements..."

      The mentioned two expressions can't be constructed using any of these.

      See full examples below:

      ------------------------- expr49626.java --------------------------
      import java.io.PrintStream;
      class A_fa32121 {
      public final int a = 0;
      public A_fa32121 next = null;
      public A_fa32121 getNext() { return next; }
      }

      public class expr49626 {
      public static void main(String argv[]) {
      System.exit(run(argv, System.out) + 95/*STATUS_TEMP*/);
      }

      public static int run(String argv[], PrintStream out) {
      A_fa32121 a_fa32121 = new A_fa32121();
      int var = 0;

      switch (var) {
      case a_fa32121.a :
      break;
      default : ;
      }
      return 0/*STATUS_PASSED*/;
      }
      }
      -----------------------------------------------------------------------------
      > /export/ld14/java/dest/jdk1.2b3L/solaris/bin/javac -d . expr49626.java
      >

      ------------------------- expr49628.java --------------------------
      import java.io.PrintStream;
      class A_fa32123 {
      public final int a = 0;
      public A_fa32123 next = null;
      public A_fa32123 getNext() { return next; }
      }

      public class expr49628 {
      public static void main(String argv[]) {
      System.exit(run(argv, System.out) + 95/*STATUS_TEMP*/);
      }

      public static int run(String argv[], PrintStream out) {
      A_fa32123 a_fa32123 = new A_fa32123();
      int var = 0;

      switch (var) {
      case a_fa32123.next.a :
      break;
      default : ;
      }
      return 0/*STATUS_PASSED*/;
      }
      }
      -----------------------------------------------------------------------------
      > /export/ld14/java/dest/jdk1.2b3L/solaris/bin/javac -d . expr49628.java
      >


      ======================================================================

      From bug 4093405:

      this.value is being allowed as a case label as well. The underlying
      cause is the same.

      todd.turnidge@Eng 1998-04-09

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              • Assignee:
                wmaddoxsunw William Maddox (Inactive)
                Reporter:
                leosunw Leo Leo (Inactive)
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                  Updated:
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