Shadowing fields with a local variable or with a method parameter is a bad practice reducing code readability: It makes it confusing to know whether the field or the variable is and should be accessed.

Noncompliant Code Example

class Foo {
  public int myField;

  public void doSomething() {
    int myField = 0;
    ...
  }

  public void doSomethingElse(int myField) {
    ...
  }
}

Exceptions

Constructors and setters are exceptions; it is common practice to name arguments for the fields the values will be assigned to. Static methods are also excepted.

class Foo {
  public int myField;

  public Foo(int myField) {
    this.myField = myField;
  }

  public static Foo build(int myField) {
    ...
  }

  public void setMyField(int myField){
    this.myField = myField;
  } 
}