Duvida com metodo equalsIgnoreCase

* @return  {@code true} if the argument is not {@code null} and it
*          represents an equivalent {@code String} ignoring case; {@code
*          false} otherwise

String  a = "teste";
if(a.equalsIgnoreCase("TESTE")){
  //retorna true
}

//se usar somente equals retorna false

if(a.equals("TESTE")){
  //retorna false
}

public boolean equalsIgnoreCase(String other){
if(other == null) return false;
return this.upperCase().equals(other.upperCase);
}