Use visitor for printing program

src/main/java/printer/ExpressionPrinter.java

@@ -0,0 +1,32 @@
+package printer;
+
+import expression.*;
+import interpreter.Visitor;
+
+public class ExpressionPrinter extends Visitor<String> {
+    private final String value;
+
+    public ExpressionPrinter(Expression expression) {
+        value = visit(expression);
+    }
+
+    public String visitAddition(Addition addition) {
+        return "(" + visit(addition.leftHandSide) + " + " + visit(addition.rightHandSide) + ")";
+    }
+
+    public String visitIdentifier(Identifier identifier) {
+        return identifier.name;
+    }
+
+    public String visitInt(Int integer) {
+        return Integer.toString(integer.value);
+    }
+
+    public String visitSubtraction(Subtraction subtraction) {
+        return "(" + visit(subtraction.leftHandSide) + " - " + visit(subtraction.rightHandSide) + ")";
+    }
+
+    public String getValue() {
+        return value;
+    }
+}

src/main/java/printer/ProgramPrinter.java

@@ -0,0 +1,36 @@
+package printer;
+
+import interpreter.Visitor;
+import program.*;
+
+public class ProgramPrinter extends Visitor<String> {
+    private final String value;
+
+    public ProgramPrinter(Program program) {
+        value = visit(program);
+    }
+
+    public String visitAssignment(Assignment assignment) {
+        ExpressionPrinter identifierPrinter = new ExpressionPrinter(assignment.identifier);
+        ExpressionPrinter expressionPrinter = new ExpressionPrinter(assignment.expression);
+        return identifierPrinter.getValue() + " := " + expressionPrinter.getValue();
+    }
+
+    public String visitComposition(Composition composition) {
+        return visit(composition.first) + " ; " + visit(composition.second);
+    }
+
+    public String visitConditional(Conditional conditional) {
+        ExpressionPrinter conditionPrinter = new ExpressionPrinter(conditional.condition);
+        return "if (" + conditionPrinter.getValue() + ") then { " + visit(conditional.thenCase) +  " } else { " + visit(conditional.elseCase) + " }";
+    }
+
+    public String visitLoop(Loop loop) {
+        ExpressionPrinter conditionPrinter = new ExpressionPrinter(loop.condition);
+        return "while (" + conditionPrinter.getValue() + ") { " + visit(loop.program) +  " }";
+    }
+
+    public String getValue() {
+        return value;
+    }
+}