Why is this an issue?

Appending String.valueOf() to a String decreases the code readability.

The argument passed to String.valueOf() should be directly appended instead.

Noncompliant code example

public void display(int i){
  System.out.println("Output is " + String.valueOf(i));    // Noncompliant
}

Compliant solution

public void display(int i){
  System.out.println("Output is " + i);                    // Compliant
}