Please have javac produce (optional!) warnings for the following
situations which are almost certainly programmer errors, or very
poor style at best:

overriding equals() but not hashCode() or vice versa
a finally clause that cannot complete normally
a member type or field that is hidden in a subclass
selecting a static member from an object value

================
I recently had a surprising bug in some of my code which might inform
the addition of a compiler warning (possibly under a "-fullwarn" option or
similar).

   public class Foo {
     public void Foo() {
            ^^^^

I accidentally added a "void" before the constructor's name, which turned the
constructor into a method, causing the object to be uninitialized.

==================
Subject:
          Proposed Lint Rules
    Date:
          Mon, 28 Jan 2002 16:36:22 -0800
   From:
          <###@###.###>
      To:
          <###@###.###>




   Not all of these are practical or advisible. Some important ones may be missing. I have not looked at the rules for C's lint, many of which may be applicable here. All of that said, this is a reasonable starting point.
 

Proposed Lint Warnings

Public or protected static method or field hidden.

More generally, anything hidden

Static method invoked via instance

return or throw within finally

"Potentially ambiguous" overloading
    Same number of args; for each arg, one is subtype of other. (I don't
    think that we can do this one: it would fire too often.)

Mixed type comparison.
  (<, ==, >, <=, >=, where primitive operands are of different type).

Public non-final field in public class.

Constructor or method whose signature differs from another only in parameter
order

Use of String(String) or Boolean(boolean).

Constructor or pseudoconstructor (clone, readObject) invokes overridable
method in same class.

Class consisting entirely of static methods with default constructor (AKA
unintentionally instantialble class).

Any use of a finalizer
    (I know this one is rather audacious)

equals overridden but not hashCode

equals(ThisType) provided but not equals(Object)

Object's toString implementation not overridden in a public class.

Concrete class implements Cloneable but does not override clone

clone method in an extendable public class does not invoke super.clone

public static final non-zero length array.

Interface consisting solely of (one or more) static fields.

nonstatic member class whose enclosing reference is never used (should be
static).

Concrete collection class as input parameter

Array-returning method returns null

Method declared to throw unchecked exception

These three are already covered by doccheck, and don't belong in compiler:
   Public or protected member missing doc comment
   Parameter of public or protected method missing doc comment
   Declared exception of public or protected method missing doc comment

Broken idioms:
Math.abs( <instance of java.util.Random>.nextInt()) % <int expression>
Math.abs( <instance of java.util.Random>.nextInt() % <int expression>)
   Should be replaced by Random.nextInt(int)

Switch statement with one or more fall-throughs

Class name begins with something other than an uppercase letter

Varibale name other than a static final begins with something other than a
lowercase letter.

Method name begins with something other than a lowercase letter

package name contains capital letters

Empty catch clause.
   (If the catch clause contains so much as a comment, this warning should not
   be emitted.)

Object.wait invoked outside of a loop

Any use of Thread.yield

Inner class implements Serializable

Class that implements Serializable does not declare serialVersionUID

Interface declares serialVersionUID

=====================================================
A class inherits a type with the same name as the class:

    package p;
    class B {
        static class A {}
    }
    class A extends B {
        // the constructor for p.A takes a
        // parameter of type p.B.A
        A(A x) {}
    }
###@###.### 10/27/04 17:27 GMT