angelosSfyr · angelosSfyr · Sep 23, 2026 · Sep 23, 2026
diff --git a/.dockerignore b/.dockerignore
@@ -0,0 +1,3 @@
+.git
+*.class
+*.ll
diff --git a/.gitattributes b/.gitattributes
@@ -0,0 +1,4 @@
+* text=auto
+*.sh text eol=lf
+Makefile text eol=lf
+*.jar binary
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
@@ -0,0 +1,15 @@
+name: tests
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Build compiler image
+        run: docker build -t minijava .
+      - name: Run test suite
+        run: docker run --rm minijava
diff --git a/.gitignore b/.gitignore
@@ -0,0 +1,10 @@
+# Build output
+*.class
+
+# Generated by JTB / JavaCC during `make compile`
+syntaxtree/
+visitor/
+MiniJavaParser*.java
+Token*.java
+ParseException.java
+JavaCharStream.java
diff --git a/CheckingVisitor.java b/CheckingVisitor.java
@@ -58,6 +58,7 @@ public String visit(ClassDeclaration n, Void argu) throws Exception {
         String classname = n.f1.accept(this, null);
         this.inClass = false;
         Main.ST.enterClass(classname);
+        n.f3.accept(this, null);
         n.f4.accept(this, null);
         return null;
     }
@@ -79,6 +80,7 @@ public String visit(ClassExtendsDeclaration n, Void argu) throws Exception {
         String parentclassName = n.f3.accept(this, null);;
         this.inClass = false;
         Main.ST.enterClass(classname);
+        n.f5.accept(this, null);
         n.f6.accept(this, null);
         return null;
     }
@@ -107,11 +109,13 @@ public String visit(MethodDeclaration n, Void argu) throws Exception {
         String myName = n.f2.accept(this, null);
         this.inClass = false;
         Main.ST.enterMethod(myName);
-        String exprType = n.f10.accept(this, null);
+        n.f7.accept(this, null);
         n.f8.accept(this, null);
-        if (!myType.equals(exprType)){
+        String exprType = n.f10.accept(this, null);
+        // the returned value must have the declared type or be a subclass of it
+        if (!myType.equals(exprType) && !Main.ST.childHasParent(exprType, myType)){
             throw new Exception("MethodDeclaration: False return type"+"("+Main.ST.getCurrentMethodName()+")");
-        }   // return statement bust be the same as the type
+        }
         Main.ST.exitMethod();
         return null;
     }
@@ -220,7 +224,22 @@ public String visit(IntegerType n, Void argu) {
     */
 
     public boolean isObject(String idType){
-        return idType != "int" && idType != "int[]" && idType != "boolean" && idType != "boolean[]";
+        return !idType.equals("int") && !idType.equals("int[]") && !idType.equals("boolean") && !idType.equals("boolean[]");
+    }
+
+    /**
+    * f0 -> "System.out.println"
+    * f1 -> "("
+    * f2 -> Expression()
+    * f3 -> ")"
+    * f4 -> ";"
+    */
+    @Override
+    public String visit(PrintStatement n, Void argu) throws Exception {
+        if (!"int".equals(n.f2.accept(this, argu))){
+            throw new Exception("PrintStatement: only integers can be printed"+"("+Main.ST.getCurrentMethodName()+")");
+        }
+        return null;
     }
 
 
@@ -240,7 +259,7 @@ public String visit(AssignmentStatement n, Void argu) throws Exception {
                 throw new Exception("AssignmentStatement: id is object but expr is not"+"("+Main.ST.getCurrentMethodName()+")");
             }
         }else{
-            if (idType != exprType){
+            if (!idType.equals(exprType)){
                 throw new Exception("AssignmentStatement: id and expr not the same type"+"("+Main.ST.getCurrentMethodName()+")");
             }
         }
@@ -260,9 +279,9 @@ public String visit(AssignmentStatement n, Void argu) throws Exception {
     * f6 -> ";"
     */
     private String arrayType(String type){
-        if (type =="boolean[]"){
+        if ("boolean[]".equals(type)){
             return "boolean";
-        }else if (type == "int[]"){
+        }else if ("int[]".equals(type)){
             return "int";
         }
         return null;
@@ -274,15 +293,15 @@ public String visit(ArrayAssignmentStatement n, Void argu) throws Exception {
         String _ret=null;
         String idType = n.f0.accept(this, argu);
         n.f1.accept(this, argu);
-        if (n.f2.accept(this, argu) != "int"){
+        if (!"int".equals(n.f2.accept(this, argu))){
             throw new Exception("ArrayAssignmentStatement: expr index is not an integer"+"("+Main.ST.getCurrentMethodName()+")");
         }
         String exprType = n.f5.accept(this, argu);    // its type must be the same as the typeOfArray
         String typeOfArray = arrayType(idType);
         if (typeOfArray == null){
-            throw new Exception("ArrayAssignmentStatement: ID IS NOT AN ARRAY"+"("+Main.ST.getCurrentMethodName()+")");
+            throw new Exception("ArrayAssignmentStatement: id is not an array"+"("+Main.ST.getCurrentMethodName()+")");
         }else{
-            if (exprType != typeOfArray){
+            if (!typeOfArray.equals(exprType)){
                 throw new Exception("ArrayAssignmentStatement: id and expr not the same type"+"("+Main.ST.getCurrentMethodName()+")");
             }
             return typeOfArray;
@@ -303,7 +322,7 @@ public String visit(IfStatement n, Void argu) throws Exception {
         String _ret=null;
         n.f0.accept(this, argu);
         n.f1.accept(this, argu);
-        if (n.f2.accept(this, argu)!="boolean"){
+        if (!"boolean".equals(n.f2.accept(this, argu))){
             throw new Exception("Not a boolean in if expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         n.f3.accept(this, argu);
@@ -325,7 +344,7 @@ public String visit(WhileStatement n, Void argu) throws Exception {
         String _ret=null;
         n.f0.accept(this, argu);
         n.f1.accept(this, argu);
-        if (n.f2.accept(this, argu)!="boolean"){
+        if (!"boolean".equals(n.f2.accept(this, argu))){
             throw new Exception("Not a boolean in while expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         n.f3.accept(this, argu);
@@ -340,12 +359,12 @@ public String visit(WhileStatement n, Void argu) throws Exception {
     @Override
     public String visit(AndExpression n, Void argu) throws Exception {
         String _ret=null;
-        if (n.f0.accept(this, argu) !="boolean"){
-            throw new Exception("Not a boolean in end expression"+"("+Main.ST.getCurrentMethodName()+")");
+        if (!"boolean".equals(n.f0.accept(this, argu))){
+            throw new Exception("Not a boolean in AND expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         n.f1.accept(this, argu);
-        if (n.f2.accept(this, argu) !="boolean"){
-            throw new Exception("Not a boolean in end expression"+"("+Main.ST.getCurrentMethodName()+")");
+        if (!"boolean".equals(n.f2.accept(this, argu))){
+            throw new Exception("Not a boolean in AND expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         return "boolean";
     }
@@ -358,11 +377,11 @@ public String visit(AndExpression n, Void argu) throws Exception {
     @Override
     public String visit(CompareExpression n, Void argu) throws Exception {
         String _ret=null;
-        if (n.f0.accept(this, argu) != "int"){
+        if (!"int".equals(n.f0.accept(this, argu))){
             throw new Exception("Not an integer in LESS expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         n.f1.accept(this, argu);
-        if (n.f2.accept(this, argu) != "int"){
+        if (!"int".equals(n.f2.accept(this, argu))){
             throw new Exception("Not an integer in LESS expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         return "boolean";
@@ -378,11 +397,11 @@ public String visit(PlusExpression n, Void argu) throws Exception {
         String _ret=null;
         String f0Str = n.f0.accept(this, argu);
         String f2Str = n.f2.accept(this, argu);
-        if (f0Str != "int"){
+        if (!"int".equals(f0Str)){
             throw new Exception("Not an integer in PLUS expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         n.f1.accept(this, argu);
-        if (f2Str != "int"){
+        if (!"int".equals(f2Str)){
             throw new Exception("Not an integer in PLUS expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         return "int";
@@ -395,11 +414,11 @@ public String visit(PlusExpression n, Void argu) throws Exception {
     @Override
     public String visit(MinusExpression n, Void argu) throws Exception {
         String _ret=null;
-        if (n.f0.accept(this, argu) != "int"){
+        if (!"int".equals(n.f0.accept(this, argu))){
             throw new Exception("Not an integer in MINUS expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         n.f1.accept(this, argu);
-        if (n.f2.accept(this, argu) != "int"){
+        if (!"int".equals(n.f2.accept(this, argu))){
             throw new Exception("Not an integer in MINUS expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         return "int";
@@ -413,11 +432,11 @@ public String visit(MinusExpression n, Void argu) throws Exception {
     @Override
     public String visit(TimesExpression n, Void argu) throws Exception {
         String _ret=null;
-        if (n.f0.accept(this, argu) != "int"){
+        if (!"int".equals(n.f0.accept(this, argu))){
             throw new Exception("Not an integer in TIMES expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         n.f1.accept(this, argu);
-        if (n.f2.accept(this, argu) != "int"){
+        if (!"int".equals(n.f2.accept(this, argu))){
             throw new Exception("Not an integer in TIMES expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         return "int";
@@ -433,14 +452,15 @@ public String visit(TimesExpression n, Void argu) throws Exception {
     public String visit(ArrayLookup n, Void argu) throws Exception {
         String _ret=null;
         String arrayType = n.f0.accept(this, argu);
-        if (arrayType != "boolean[]" && arrayType != "int[]"){
-            throw new Exception("Not an array identigier in ArrayLookup expression"+"("+Main.ST.getCurrentMethodName()+")");
+        if (!"boolean[]".equals(arrayType) && !"int[]".equals(arrayType)){
+            throw new Exception("Not an array in ArrayLookup expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         n.f1.accept(this, argu);
-        if (n.f2.accept(this, argu) != "int"){
+        if (!"int".equals(n.f2.accept(this, argu))){
             throw new Exception("Not an integer in ArrayLookup expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
-        if (arrayType=="int[]") return "int";
+        Main.ST.setArrayLookupType(n, arrayType);
+        if ("int[]".equals(arrayType)) return "int";
         return "boolean";
     }
 
@@ -453,8 +473,8 @@ public String visit(ArrayLookup n, Void argu) throws Exception {
     public String visit(ArrayLength n, Void argu) throws Exception {
         String _ret=null;
         String arrayType = n.f0.accept(this, argu);
-        if (arrayType != "int[]" && arrayType != "boolean[]"){
-            throw new Exception("Not an array id  in ArrayLength expression"+"("+Main.ST.getCurrentMethodName()+")");
+        if (!"int[]".equals(arrayType) && !"boolean[]".equals(arrayType)){
+            throw new Exception("Not an array in ArrayLength expression"+"("+Main.ST.getCurrentMethodName()+")");
         }
         n.f1.accept(this, argu);
         n.f2.accept(this, argu);
@@ -557,7 +577,11 @@ public String visit(PrimaryExpression n, Void argu) throws Exception {
     */
     @Override
     public String visit(IntegerLiteral n, Void argu) throws Exception {
-        n.f0.accept(this, argu);
+        try {
+            Integer.parseInt(n.f0.toString());
+        } catch (NumberFormatException ex) {
+            throw new Exception("IntegerLiteral: " + n.f0.toString() + " is out of range"+"("+Main.ST.getCurrentMethodName()+")");
+        }
         return "int";
     }
 
@@ -601,8 +625,8 @@ public String visit(ThisExpression n, Void argu) throws Exception {
    public String visit(IntegerArrayAllocationExpression n, Void argu) throws Exception {
       String _ret=null;
       String f3type = n.f3.accept(this, argu);
-      if (f3type != "int"){
-        throw new Exception("Array size is not na integer"+"("+Main.ST.getCurrentMethodName()+")");
+      if (!"int".equals(f3type)){
+        throw new Exception("Array size is not an integer"+"("+Main.ST.getCurrentMethodName()+")");
       }
       return "int[]";
    }
@@ -617,8 +641,8 @@ public String visit(IntegerArrayAllocationExpression n, Void argu) throws Except
     public String visit(BooleanArrayAllocationExpression n, Void argu) throws Exception {
         String _ret=null;
         String f3type = n.f3.accept(this, argu);
-        if (f3type != "int"){
-            throw new Exception("Array size is not na integer"+"("+Main.ST.getCurrentMethodName()+")");
+        if (!"int".equals(f3type)){
+            throw new Exception("Array size is not an integer"+"("+Main.ST.getCurrentMethodName()+")");
         }
         return "boolean[]";
     }
@@ -639,7 +663,7 @@ public String visit(AllocationExpression n, Void argu) throws Exception {
         String className = n.f1.accept(this, argu);
         this.inClass = false;
         if (!Main.ST.existsClass(className)){
-            throw new Exception("Class+ "+className+" does not exist"+"("+Main.ST.getCurrentMethodName()+")");
+            throw new Exception("Class "+className+" does not exist"+"("+Main.ST.getCurrentMethodName()+")");
         }
         return className;
     }
@@ -649,10 +673,17 @@ public String visit(AllocationExpression n, Void argu) throws Exception {
     @Override
     public String visit(Identifier n, Void argu) throws Exception {
         String idName =  n.f0.toString();
-        if (this.inClass == false){
-            return  Main.ST.lookup(idName);
-        } 
-        return idName;
+        if (this.inClass){
+            return idName;
+        }
+        String type = Main.ST.lookup(idName);
+        if (type == null){
+            throw new Exception("Undefined identifier: " + idName + "("+Main.ST.getCurrentMethodName()+")");
+        }
+        if (type.equals(SymbolTable.MAIN_ARGS_TYPE)){
+            throw new Exception("The argument of main cannot be used: " + idName + "("+Main.ST.getCurrentMethodName()+")");
+        }
+        return type;
     }
 
     /**
@@ -663,7 +694,7 @@ public String visit(Identifier n, Void argu) throws Exception {
     public String visit(NotExpression n, Void argu) throws Exception {
         String _ret=null;
         n.f0.accept(this, argu);
-        if (n.f1.accept(this, argu) != "boolean"){
+        if (!"boolean".equals(n.f1.accept(this, argu))){
             throw new Exception("NotExpression: primary expression is not a boolean"+"("+Main.ST.getCurrentMethodName()+")");
         }
         return "boolean";

diff --git a/Dockerfile b/Dockerfile
@@ -0,0 +1,14 @@
+# Builds the MiniJava compiler and includes clang to compile/run the generated LLVM IR.
+# clang 14 (Ubuntu 22.04) is used because the generated IR uses typed pointers (i8*),
+# which newer LLVM versions no longer support.
+FROM eclipse-temurin:17-jdk-jammy
+
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends clang make \
+ && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+COPY . .
+RUN make compile
+
+CMD ["./run_tests.sh"]
-Original file line number
+Diff line change
@@ -0,0 +1,3 @@
+    .git
+    *.class
+    *.ll