[java] SingularField false positive with non static inner classes

[arturbosch]

Affects PMD Version: 6.11.0

Rule: SingularField

Description: Suggests to move the field value to local var even if it is used from an inner class instance with A.this.value.

Code Sample demonstrating the issue:

class A {

    private String value;
    private String derivedValue;

    public A(String value) {
        this.value = value;
        this.derivedValue = this.value + "-more";
    }

    private void run() {
        final B b = new B();
        b.useA();
    }

    public static void main(String[] args) {
        new A("").run();
    }

    public class B {

        public void useA() {
            final String field = A.this.value;
            System.out.println(field);
        }
    }
}

Running PMD through: CLI