ADDITIONAL SYSTEM INFORMATION :
Tested in Linux using java 11 but it probably happens in all versions of java

A DESCRIPTION OF THE PROBLEM :
If a library has a method with return type T and changes it to return type T2 that extends T (i.e. T2 IS-A T by definition of inheritance), Java throws a NoSuchMethodError

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Create 2 versions of a given lib (source code in the source code section).
- Compile and create a lib_v1.jar
- Compile and create a lib_v2.jar

Now, lets create an application that uses the lib.

import lib.*;

public class Main {
  public static void main(String args[]) {
    A a = new A();
    a.get().m();
  }
}

Compile using lib_v1.jar. It will execute correctly. Without recompiling, execute using lib_v2.jar.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
It should execute and show "Extended Base class" in the console
ACTUAL -
Exception in thread "main" java.lang.NoSuchMethodError: 'lib.BaseClass lib.A.get()'
at Main.main(Main.java:6)


---------- BEGIN SOURCE ----------
lib v1:

package lib;

public class BaseClass {
  public void m() {
    System.out.println("Base class");
  }
}

package lib;

public class A {
  public BaseClass get() {
    return new BaseClass();
  }
}


lib v2:

package lib;

public class A {
  public ExtendedBaseClass get() {
    return new ExtendedBaseClass();
  }
}


package lib;

public class BaseClass {
  public void m() {
    System.out.println("Base class");
  }
}


Create a new application that uses that lib:

import lib.*;

public class Main {
  public static void main(String args[]) {
    A a = new A();
    a.get().m();
  }
}

package lib;

public class ExtendedBaseClass extends BaseClass {
  public void m() {
    System.out.println("Extended Base class");
  }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
If we have access to the source code, recompile against the new version of the lib. But if we don't it means we can't upgrade the library (could be a library used by another library).

FREQUENCY : always