Added Lexemes

Wrote some literals and keywords.

lexerA1.g4

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+lexer grammar lexerA1;
+
+// Literals
+IntigerLiteral: ;
+
+FloatingPointLiteral: ;
+
+CharacterLiteral: '\'' SingleCharacter '\'' | '\'' EscapeSequence '\'';
+
+fragment SingleCharacter:
+    [^'\\];
+
+StringLiteral: '"' StringCharacters? '"';
+
+fragment StringCharacters:
+    StringCharacter+;
+
+fragment StringCharacter:
+    [^"\\] | EscapeSequence;
+
+fragment EscapeSequence:
+    '\\' ('u0008' | 'u0009' | 'u000a' | 'u000c' | 'u000d' | 'u0022' | 'u0027' | 'u005c' | OctalEscape);
+
+fragment OctalEscape:
+    '\\' OctalDigit | '\\' OctalDigit OctalDigit | '\\' ZeroToThree OctalDigit OctalDigit;
+
+fragment OctalDigit:
+    [0-7];
+
+fragment ZeroToThree:
+    [0-3];
+
+BooleanLiteral: 'true' | 'false' ;
+
+NullLiteral: 'null';
+// Keywords
+Public : 'public';
+Protected: 'protected';
+Private: 'private';
+Static: 'static';
+Abstract: 'abstract';
+Final: 'final';
+Native: 'native';
+Synchronized: 'synchronized';
+Transient: 'transient';
+Volatile: 'volatile';
+Strictfp: 'strictfp';
+Assert: 'Assert';