19.1.3

Problem #3: Field Declaration versus Method Declaration

LALR(1) GRAMMAR

public static int maddie(String art) { return art.length(); }

Therefore, the parser cannot tell with only one token lookahead whether

static

(or, similarly,

public

) should be reduced to

FieldModifier

 or

MethodModifier

.

Therefore, the productions shown above result in a grammar that is not LALR(1).

There are also other problems with drawing distinctions among different kinds of

modifiers in the grammar.

While not all contexts provoke the problem, the simplest solution is to com 

bine all contexts in which such modifiers are used, eliminating all six of the

nonterminals

ClassModifiers

( 8.1.2),

FieldModifiers

( 8.3.1),

MethodModifiers

( 8.4.3),

ConstructorModifiers

( 8.6.3),

InterfaceModifiers

( 9.1.2), and

ConstantModifiers

( 9.3) from the grammar, replacing them all with a single non 

terminal

Modifiers

:

Modifiers:

Modifier

Modifiers Modifier

Modifier: one of

public protected private

static

abstract final native synchronized transient volatile

A later stage of compiler analysis then sorts out the precise role of each modifier

and whether it is permitted in a given context.

19.1.3   Problem #3: Field Declaration versus Method Declaration

Consider the two productions (shown after problem #2 has been corrected):

FieldDeclaration:

Modifiers

opt

Type VariableDeclarators

 ;

and:

MethodHeader:

Modifiers

opt

ResultType MethodDeclarator Throws

opt

where

ResultType

 is defined as:

436