Java 1.7 if语句，用于声明和初始化带有if语句范围的变量的结果

Question

Yarh- this is hard to explain. Is it possible to so something like this:

static String nullOrLastname(String name)
{
    if(name.equals("jonas")) return "marshen";
    return null;
} 

if( (String lastname=nullOrLastname("jonas")) != null)
{   
     System.out.println(lastname);
}

This works, but is ugly etc.

for(String  lastname = nullOrLastname("jonas");lastname !=null;lastname=null)
{
    System.out.println(lastname);
}

Is there a better way? What is the name of what I want to do? Did I use the correct words in the headline?

Answer 1

I would do the following if you don't want scope leak.

{
    String lastname = nullOrLastname("jonas");
    if (lastname != null)
        System.out.println(lastname);
}

In Java 8 you would use an Optional and turn this into a one liner.

static Optional<String> nullOrLastname(String name)    {
    return Optional.ofNullable("jonas".equals(name) ? "marshen" : null);
}

public static void main(String[] args) {
    nullOrLastname("jonas").ifPresent(System.out::println);
}

Answer 2

You need to declare the variable first:

String lastname;
if( (lastname=nullOrLastname("jonas")) != null)
{   
     System.out.println(lastname);
}