The toString method is defined in the java.lang.Object class and returns the object class name and its internal address:

public String toString() {
    return getClass().getName() + "@" + Integer.toHexString(hashCode());
}

The java.util.Objects class provides utility methods to get the string value code of an object:

public static String toString(Object o) {
    return String.valueOf(o);
}

public static String toString(Object o, String nullDefault) {
    return (o != null) ? o.toString() : nullDefault;
}

The java.util.Arrays class provides utility methods to get the string value of an array of objects (including specific overloaded methods for each primitive type). It also provides a utility method to get a deep string value of an array of objects (array of arrays).

The following is a sample code that show how to implement the toString method.

• Superclass "P":
  

  class P {
      Integer id = 1;
  
      @Override
      public String toString() {
          String value = "%s@%X (id:%d)";
          return String.format(Locale.getDefault(), value, getClass().getName(), System.identityHashCode(this), id);
      }
  }

• Subclass "C":
  

  class C extends P {
      String code = "default";
  
      @Override
      public String toString() {
          String value = "%s (code:%s)";
          return String.format(Locale.getDefault(), value, super.toString(), code);
      }
  }