Add java code and test cases

compiler/target/test-classes/examples/functions/int_parameters

@@ -0,0 +1,5 @@
+int add(int a, int b) {
+    return a + b;
+}
+
+println(add(5, 8));

compiler/target/test-classes/examples/functions/scopes

@@ -0,0 +1,9 @@
+int i;
+i = 42;
+int randomNumber() {
+	int i;
+	i = 4;
+	return i;
+}
+println(randomNumber());
+println(i);

compiler/target/test-classes/examples/functions/simple_function

@@ -0,0 +1,5 @@
+int number() {
+    return 4;
+}
+
+println(number());