Get empty string when null

I want to get string values of my fields (they can be type of long string or any object),

if a field is null then it should return empty string, I did this with guava;

nullToEmpty(String.valueOf(gearBox))
nullToEmpty(String.valueOf(id))
...

But this returns null if gearbox is null! Not empty string because valueOf methdod returns string "null" which leads to errors.

Any Ideas?

EDIt: there are 100s fields I look for something easy to implement

You can use Objects.toString() (standard in Java 7):

Objects.toString(gearBox, "")

Objects.toString(id, "")

---

From the linked documentation:

>public static String toString(Object o, String nullDefault)

> >Returns the result of calling toString on the first argument if the first argument is not null and returns the second argument otherwise.

> >Parameters:
o - an object
nullDefault - string to return if the first argument is null

> >Returns:
the result of calling toString on the first argument if it is not null and the second argument otherwise.

> >See Also:
toString(Object)

For java 8 you can use Optional approach:

Optional.ofNullable(gearBox).orElse("");
Optional.ofNullable(id).orElse("");

If you don't mind using Apache commons, they have a StringUtils.defaultString(String str) that does this.

> Returns either the passed in String, or if the String is null, an empty String ("").

If you also want to get rid of "null", you can do:

StringUtils.defaultString(str).replaceAll("^null$", "")

or to ignore case:

StringUtils.defaultString(str).replaceAll("^(?i)null$", "")

If alternative way, Guava provides Strings.nullToEmpty(String).

Source code

String str = null;
str = Strings.nullToEmpty(str);
System.out.println("String length : " + str.length());

Result

0

Use an inline null check

gearBox == null ? "" : String.valueOf(gearBox);

StringUtils.defaultString(String str) Returns either the passed in String, or if the String is null, an empty String ("").

Example from java doc > StringUtils.defaultString(null) will return "" > StringUtils.defaultString("") will return "" > StringUtils.defaultString("bat") will return "bat"

Since you're using guava:

Objects.firstNonNull(gearBox, "").toString();

In Java 9+ use : Objects.requireNonNullElse (obj, defaultObj) https://docs.oracle.com/javase/9/docs/api/java/util/Objects.html#requireNonNullElse-T-T-

//-- returns empty string if obj is null
Objects.requireNonNullElse (obj, "")