Method for String Building in java

Question

I have written a custom method to use StringBuilder in java. My Requirement is to create a method which accepts any number of arguments of any type and return String by concatenating the arguments.

eg. msgBuilder("Hello ",0," how"," are"," you ",2.5) return "Hello 0 how are you 2.5"

Here is my java code. Please Someone review my code and suggest If I did anything is wrong or Can I use this further in my projects.

        public class Test {
            public static void main(String[] args ){
                String msg = msgBuilder("Hello ",5," How ","are ","you");
                System.out.println(msg);
            }

            private static String msgBuilder(Object... params){
                StringBuilder sb = new StringBuilder();
                for(Object obj:params){
                    sb.append(obj);
                }
                return sb.toString();
            }
        }

Answer 1

I had this in mind:

private static String msgBuilder(Object... params) {
    StringBuilder sb = new StringBuilder();

    if (params.length > 0) {
        sb.append(params[0]);
    }

    for (int i = 1; i < params.length; ++i) {
        sb.append(" ").append(params[i]);
    }

    return sb.toString();
}

The above version allows you not to hardcode the white space delimiting your tokens. Instead of saying

String msg = msgBuilder("Hello ", 5, " How ", "are ", "you");

you can say succintly

String msg = msgBuilder("Hello", 5, "How", "are", "you");

Hope that helps.

Answer 2

Your approach

As pointed out by the other answers, you are practically hard-coding whitespaces in your arguments, which can get non-standard easily, even in your example. Otherwise, the use of StringBuilder is sound, although it wouldn't deal nicely with a single null value - the for-each loop will fail as it implicitly tries to get an Iterator for it.

Java 8

An alternative is to rely on the stream-based processing that Java 8 offers:

private static String format(Object... values) {
    if (values == null) {
        return "";
    }
    return Arrays.stream(values)
                    .map(Objects::toString)
                    .collect(Collectors.joining(" "));
}

1. Construct a Stream<Object> from values using Arrays.stream(T...).
2. map() each value using Objects.toString(Object) as a method reference.
3. collect() the stream into a String by joining(" ") them together.

Answer 3

I just decompiled the below code in java version "1.8.0_73" and found that compiler is automatically optimizing the code for strings

            String hello = "a" + "b" + "c" + " hello " + " world ";
            System.out.println("Hello World!!");

            String a="a";
            String b="b";
            String c="c";
            String d=a+b+c;
            System.out.println(d);  
            System.out.println(a +" yo "+ b); 

Code after decompiling

            String s = "abc hello  world ";
            System.out.println("Hello World!!");
            String s1 = "a";
            String s2 = "b";
            String s3 = "c";
            String s4 = (new StringBuilder()).append(s1).append(s2).append(s3).toString();
            System.out.println(s4);
            System.out.println((new StringBuilder()).append(s1).append(" yo ").append(s2).toString());

Answer 4

@coderodde has a good point about eliminating the need for white space.

I'd simply do it this way:

private static String buildString(Object... values) {
        if (values.length == 0) {
             return "";
        }
        StringBuilder result = new StringBuilder();
        for (Object value : values) {
            result.append(' ').append(value);
        }
        return result.substring(1);
}