passing a String array as argument

Question

A String array can be declared and initialized in the following way:

String[] str = {"A", "B"};

but for a method which accepts a String array as argument, why can't the same be used there?

For example: if in the code below, i replace the call to show() from show(str); to show({"A" "B"});, it shows complier error. Why?

public class StringArray {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String[] str = {"A", "B"};
        show(str);
    }
    static void show(String[] s) {
        System.out.println(s[0] + s[1]);
    }
}

The compiler errors shown are:

StringArray.java:9: illegal start of expression
                show({"A", "B"});
                     ^
StringArray.java:9: ';' expected
                show({"A", "B"});
                      ^
StringArray.java:9: illegal start of expression
                show({"A", "B"});
                         ^
StringArray.java:9: ';' expected
                show({"A", "B"});
                          ^
StringArray.java:9: illegal start of type
                show({"A", "B"});
                               ^
StringArray.java:11: class, interface, or enum expected
        static void show(String[] s) {
               ^
StringArray.java:13: class, interface, or enum expected
        }
        ^
7 errors

Also using show(new String[] {"A", "B"}); is allowed. How is new String[]{"A", "B"} different from {"A", "B"} when passing them as method arguments? Thanx in advance!

Answer 1

The syntax {"A", "B"} (without new String[] in front of it) can only be used as an array initializer expression. In all other contexts (including method calls), you need to use the new operator.

See the Java Tutorial on Arrays for more info.

Answer 2

String[] str = {"A", "B"}; is minified version of String[] str = new String[]{"A", "B"};, Compiler doesn't know about plain {"A", "B"} as a string array unless you explicitly mention.