Java - Check Not Null Empty else assign default value

Question

I am trying to simplify the following code   The basic steps that the code should carry out are as follows    Assign String a default value  Run a method  If the method returns a null empty string leave the String as default  If the method returns a valid string set the String to this result   A Simple example would be       String temp   System getProperty  XYZ        String result    default       if temp    null  amp  amp   temp isEmpty             result   temp          I have made another attemp using a ternary operator       String temp      String result   isNotNullOrEmpty temp   System getProperty  XYZ      temp    default     The isNotNullOrEmpty   Method   private static boolean isNotNullOrEmpty String str       return  str    null  amp  amp   str isEmpty         Is it possible to do all of this in-line  I know I could do something like this   String result   isNotNullOrEmpty System getProperty  XYZ      System getProperty  XYZ      default     But I am calling the same method twice  I would be something like to do something like this  which doesn t work    String result   isNotNullOrEmpty String temp   System getProperty  XYZ      temp    default     I would like to initialize the  temp  String within the same line  Is this possible  Or what should I be doing   Thank you for your suggestions   Tim

User · Answer

Sounds like you probably want a simple method like this:

public String getValueOrDefault(String value, String defaultValue) {
    return isNotNullOrEmpty(value) ? value : defaultValue;
}

Then:

String result = getValueOrDefault(System.getProperty("XYZ"), "default");

At this point, you don't need temp... you've effectively used the method parameter as a way of initializing the temporary variable.

If you really want temp and you don't want an extra method, you can do it in one statement, but I really wouldn't:

public class Test {
    public static void main(String[] args) {
        String temp, result = isNotNullOrEmpty(temp = System.getProperty("XYZ")) ? temp : "default";
        System.out.println("result: " + result);
        System.out.println("temp: " + temp);
    }

    private static boolean isNotNullOrEmpty(String str) {
        return str != null && !str.isEmpty();
    }
}

User · Answer

You can use this method in the ObjectUtils class from org apache commons lang3 library    public static  lt T gt  T defaultIfNull T object  T defaultValue

User · Answer

With guava you can use   MoreObjects firstNonNull possiblyNullString  defaultValue

User · Answer

In Java 9  if you have an object which has another object as property and that nested objects has a method yielding a string  then you can use this construct to return an empty string if the embeded object is null   String label   Optional ofNullable org getDiffusion    map Diffusion  getLabel  orElse  quot  quot    In this example    org is an instance of an object of type Organism Organism has a Diffusion property  another object  Diffusion has a String label property  and getLabel   getter    With this example  if org getDiffusion   is not null  then it returns the getLabel property of its Diffusion object  this returns a String    Otherwise  it returns an empty string

User · Answer

I know the question is really old  but with generics one can add a more generalized method with will work for all types   public static  lt T gt  T getValueOrDefault T value  T defaultValue        return value    null   defaultValue   value

User · Answer

If using JDK 9    use Objects requireNonNullElse T obj  T defaultObj

User · Answer

Use Java 8 Optional  no filter needed    public static String orElse String defaultValue      return Optional ofNullable System getProperty  property    orElse defaultValue

User · Answer

This is the best solution IMHO    It covers BOTH null and empty scenario  as is easy to understand when reading the code    All you need to know is that  getProperty returns a null when system prop is not set   String DEFAULT XYZ   System getProperty  user home       xyz   String PROP   Optional ofNullable System getProperty  XYZ             filter s - gt   s isEmpty             orElse DEFAULT XYZ

User · Answer

Use org apache commons lang3 StringUtils String emptyString   new String        result   StringUtils defaultIfEmpty emptyString   quot default quot    System out println result    String nullString   null  result   StringUtils defaultIfEmpty nullString   quot default quot    System out println result    Both of the above options will print   default default

[java] Java - Check Not Null/Empty else assign default value

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