Why I cannot run this java foo.class file in MATLAB

Question

I have compiled the following java file, and added the file path to the classpath. But after calling the class it shows some errors. As I'm new in Java, please help me.

MyQueue2.java

import java.util.PriorityQueue;
import java.util.*;

public class MyQueue2 {
  Comparator<Double> c;
  PriorityQueue<Double> PQ;

  public MyQueue2() {
    c = new Comparator<Double>(){
            public int compare(Double o1, Double o2){
              if(o2 > o1) {
                return -1;
              } else if(o1 > o2) {
                return 1;
              } else {
                return 0;
              }
            }
        };
    PQ = new PriorityQueue<Double>(1000,c);
  }

  public void addElement(double d) {
    PQ.add(d);
  }

  public double removeElement() {
    return(PQ.remove());
  }
}

My commands in MATLAB:

import java.util.PriorityQueue;
import java.util.*;
import MyQueue2;
methods('MyQueue2') %

Methods for class MyQueue2:

MyQueue2       equals         hashCode       notifyAll      toString       
addElement     getClass       notify         removeElement  wait    

a = MyQueue2

Java exception occurred:
java.lang.NoClassDefFoundError: MyQueue2$1

    at MyQueue2.<init>(MyQueue2.java:9)

Caused by: java.lang.ClassNotFoundException: MyQueue2$1

    at java.net.URLClassLoader$1.run(Unknown Source)

    at java.security.AccessController.doPrivileged(Native Method)

    at java.net.URLClassLoader.findClass(Unknown Source)

    at com.mathworks.jmi.CustomURLClassLoader.findClass(ClassLoaderManager.java:760)

    at java.lang.ClassLoader.loadClass(Unknown Source)

    at java.lang.ClassLoader.loadClass(Unknown Source)

    at java.lang.ClassLoader.loadClassInternal(Unknown Source)

    ... 1 more

b = MyQueue2    % again

Java exception occurred:
java.lang.NoClassDefFoundError: MyQueue2$1

    at MyQueue2.<init>(MyQueue2.java:9)

Please help me to solve the problem.

I am not matlab guru, but I have some suggestion for you :1. add a package name; 2. build a jar file to include both class file; 3. put the jar in the classpath. If you can still find the MyQueue2 class, that should be ok for MyQueue2$1.class — Harry.Chen
– Harry.Chen, Commented Aug 6, 2013 at 9:54

Harry.Chen · Accepted Answer · 2013-08-06 09:43:50Z

1

After you compile the MyQueue2.java , you should get 2 class file MyQueue2.class and MyQueue2$1.class--which is for the anonymous class generated for Comparator , did u put them all in the classpath ? I guess you forgot this.

answered Aug 6, 2013 at 9:43

Harry.Chen

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1 Comment

remo Over a year ago

Yes, I have added the new $1.class file in the same forlder. But It shows the same error

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