No Class Def Found Error

Question

Im getting the java.lang.NoClassDefFoundError exception when i run the program. I have tried it on multiple computers and still get the same error. I have the classes defined I still can find the error can anyone help me?

public class PostfixDriver {
  public static void main(String[] args) {
 System.out.println("Testing postfix expressions with\n" +
  "a = 2.0, b = 3.0, c = 4.0, d = 5.0\n");
  testPostfix("a+b");
 testPostfix("a-b+c*d");
  testPostfix("(a+b)*c-d");
   testPostfix("a+b*(c-d)");
 testPostfix("(a+b)/(c-d)");
  testPostfix("a*(b/(c-d))");
 } // end main

 public static void testPostfix(String infixExpression) {
String postfixExpression = Postfix.convertToPostfix(infixExpression);
 System.out.println("Infix: " + infixExpression);
System.out.println("Postfix: " + postfixExpression);
  System.out.println("Value: " + 
Postfix.evaluatePostfix(postfixExpression));
  System.out.println();
  } // end testPostfix
  } // end PostfixDriver

this is the full error

Exception in thread "main" java.lang.NoClassDefFoundError: Postfix
at PostfixDriver.testPostfix(PostfixDriver.java:17)
at PostfixDriver.main(PostfixDriver.java:8)
Caused by: java.lang.ClassNotFoundException: Postfix
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)

It is saying it is coming from Postfix which is the class that has the converttoPostfix and all that is the same.. I can post it if needed.

Postfix.java

 public static String convertToPostfix(String infix) {
  ArrayStack operator = new ArrayStack();
  String item;
  String postfixe;
  Object top;



  for(int i = 0; infix.length() >= 0; i++){
   item.charAt(i);  


  if (Postfix.isVariable(item.charAt(i))){
    postfixe.concat(item.toString());        
  }

  else if (item.charAt(i) == '('){
     operator.push(item);
  }
  else if (item.charAt(i) == ')'){
     Postfix.concat(item.toString()); 
     while(!top.equals('(')){
        postfixe.concat(item.toString()); 
        top = operator.pop();
     }
  }
  else {
     while(!operator.isEmpty()){
        top = operator.peek();

        if(Postfix.getPrecedence(item.charAt(i)) <= (Character)top){
           postfixe.concat(item);
           operator.pop();
        }
        else {
           break;   
        }
       operator.push(item);

     } 
  }


  }

while(!operator.isEmpty()){
  top = operator.pop();
  Postfix.concat(item);

  } 

  return postfixe;







   } // end convertToPostfix

Possible duplicate of [Why am I getting a NoClassDefFoundError in Java?](https://stackoverflow.com/questions/34413/why-am-i-getting-a-noclassdeffounderror-in-java) — Philipp Claßen, Jun 14 '17 at 21:23

score 0 · Accepted Answer · answered Jun 14 '17 at 21:19

I can only guess, but does your Postfix class contain static fields or static initialization blocks? If an error is thrown there, you get the notorious NoClassDefFoundError.

Beside that, to cite from Why am I getting a NoClassDefFoundError in Java?:

This is caused when there is a class file that your code depends on and it is present at compile time but not found at runtime. Look for differences in your build time and runtime classpaths.

But note that it does not always have to do with classpath errors:

See the other answer, for more details:

... The point is, a NoClassDefFoundError is not necessarily a classpath problem.

No Class Def Found Error

1 Answers1