implement grammar and grammarrule

src/main/java/parser/grammar/Grammar.java

@@ -0,0 +1,43 @@
+package parser.grammar;
+
+import java.util.Set;
+
+public class Grammar {
+
+    private final Set<String> terminals;
+    private final Set<String> nonterminals;
+    private final String startSymbol;
+    private final String epsilonSymbol;
+
+    private final Set<GrammarRule> rules;
+
+    public Grammar(Set<String> terminals, Set<String> nonterminals,
+                   String startSymbol, String epsilonSymbol,
+                   Set<GrammarRule> rules) {
+        this.terminals = terminals;
+        this.nonterminals = nonterminals;
+        this.startSymbol = startSymbol;
+        this.epsilonSymbol = epsilonSymbol;
+        this.rules = rules;
+    }
+
+    public Set<String> getTerminals() {
+        return this.terminals;
+    }
+
+    public Set<String> getNonterminals() {
+        return this.nonterminals;
+    }
+
+    public String getStartSymbol() {
+        return this.startSymbol;
+    }
+
+    public String getEpsilonSymbol() {
+        return this.epsilonSymbol;
+    }
+
+    public Set<GrammarRule> getRules() {
+        return this.rules;
+    }
+}

src/main/java/parser/grammar/GrammarRule.java

@@ -0,0 +1,20 @@
+package parser.grammar;
+
+public class GrammarRule {
+
+    private final String leftside;
+    private final String rightside;
+
+    public GrammarRule(String leftside, String... rightside) {
+        this.leftside = leftside;
+        this.rightside = String.join(" ", rightside);
+    }
+
+    public String getLeftside() {
+        return this.leftside;
+    }
+
+    public String getRightside() {
+        return this.rightside;
+    }
+}