EBNF Grammar for Mini-Java

Goal = MainClass, { ClassDeclaration }, EOF;
MainClass = "class", Identifier, "{", "public", "static", "void", "main", "(", "String", "[", "]", Identifier, ")", "{", Statement, "}", "}";
ClassDeclaration = "class", Identifier, [ "extends", Identifier ], "{", { VarDeclaration }, { MethodDeclaration } "}";
VarDeclaration = Type, Identifier, ";";
MethodDeclaration = "public", Type, Identifier, "(", [ Type, Identifier, { ",", Type, Identifier }, ], ")", "{", { VarDeclaration }, { Statement }, "return", Expression, ";", "}";
Type = "int", "[", "]"
| "boolean"
| "int"
| Identifier
;
Statement = "{", { Statement }, "}"
| "if", "(", Expression, ")", Statement, "else", Statement
| "while", "(", Expression, ")", Statement
| "System.out.println", "(" , Expression, ")", ";"
| Identifier, "=", Expression, ";"
| Identifier, "[", Expression, "]", "=", Expression, ";"
;
Expression = Expression , ( "&&" | "<" | "+" | "-" | "*" ) , Expression
| Expression, "[", Expression, "]"
| Expression, ".", "length"
| Expression, ".", Identifier, "(", [ Expression { ",", Expression } ], ")"
| IntegerLiteral
| "true"
| "false"
| Identifier
| "this"
| "new", "int", "[", Expression, "]"
| "new", Identifier ,"(" ,")"
| "!", Expression
| "(", Expression, ")"
;
Identifier is one or more letters, digits, and underscores, starting with a letter
IntegerLiteral is one or more decimal digits
EOF is a distinguished token returned by the scanner at end-of-file

Comments

Comments are // to end of line and /* ... */, just as in Java. The /* ... */ comments do not nest in Java. For example, 
/*
            One commment
            /*  Nested comment */
            Bad things will happen
            */
The second /* will be ignored (it is in a comment), and the first */ will terminate the comment. Now, "bad things will happen" as the remaining text is not a comment.

Appel, 2nd edition, page 484, describes comments in MiniJava as being nestable. This is an interesting exercise for the scanner, but is not required.

EBNF

ISO/IEC 14977: 1996(E)
  • Terminal symbols are quoted
  • [ and ] indicate optional symbols
  • { and } indicate repetition
  • ( and ) group items together; the other brackets do too