@@ -0,0 +1,224 @@
+package net.zero918nobita.smilepp.frontend;%0A%0Apublic class Variable extends Expression %7B%0A  private String name;%0A%0A  public Variable(String name) %7B%0A    this.name = name;%0A  %7D%0A%0A  public String toString() %7B%0A    return name;%0A  %7D%0A%7D%0A

Add `Variable` class