Java Equivalents of C# String.Format() and String.Join()

Java equivalents of C# String.Format() and String.Join()

The Java String object has a format method (as of 1.5), but no join method.

To get a bunch of useful String utility methods not already included you could use org.apache.commons.lang.StringUtils.

String.Format (.NET) equivalent in Java?

The other suggestions are certainly good, but are more in the style of printf and its lineage which are more recent additions to Java. The code you posted looks to be inspired by MessageFormat.

String format = "Test: {0}, {1}"
System.out.println(MessageFormat.format(format, "Text1", "Text2"))

I'm not really certain about what the 'Return: statement is doing though.

Java: convert ListString to a join()d String

String.join

With Java 8 you can do this without any third party library.

If you want to join a Collection of Strings you can use the String.join() method:

List<String> list = Arrays.asList("foo", "bar", "baz");
String joined = String.join(" and ", list); // "foo and bar and baz"

Collectors.joining

If you have a Collection with another type than String you can use the Stream API with the joining Collector:

List<Person> list = Arrays.asList(
  new Person("John", "Smith"),
  new Person("Anna", "Martinez"),
  new Person("Paul", "Watson ")
);

String joinedFirstNames = list.stream()
  .map(Person::getFirstName)
  .collect(Collectors.joining(", ")); // "John, Anna, Paul"

The StringJoiner class may also be useful.

String Array to String

String[] start = {"first", "second", "third"};
String addedTogether = Arrays.toString(start);

System.out.println(addedTogether);
//prints [first, second, third]

delimeter in String.Join()

It works, but the String is immutable. The method replaceAll(..) returns the new String itself with replacement and you need to assign it to a variable.

String helper = "a,b"; 
String temp = "','";
helper = helper.replaceAll(",",temp);

Fastest way to put contents of SetString to a single String with words separated by a whitespace?

With commons/lang you can do this using StringUtils.join:

String str_1 = StringUtils.join(set_1, " ");

You can't really beat that for brevity.

Update:

Re-reading this answer, I would prefer the other answer regarding Guava's Joiner now. In fact, these days I don't go near apache commons.

Another Update:

Java 8 introduced the method String.join()

String joined = String.join(",", set);

While this isn't as flexible as the Guava version, it's handy when you don't have the Guava library on your classpath.

unexpected String.join() behavior

You're iterating over the list, and calling String.join with a single entry each time. That's never going to use the delimiter.

To make this clear, consider these two examples:

String x1 = String.join(",", "a");
String x2 = String.join(",", "a", "b");

Then the value of x1 will be "a", and the value of x2 will be "a,b". String.join only adds the delimiter between items - so if you only pass it a single item, it doesn't need to add any delimiters.

You can just remove your for loop, and replace it with:

System.out.println(String.join(",", str));

String.Format vs ToString()

I did a little benchmark in Linqpad:

void Main()
{
    int iterations = 1000000;
    decimal d = 12.0m;
    var text = "";

    var sw = Stopwatch.StartNew();
    for (int i = 0; i < iterations; i++)
    {
        // 1. how I'd have done it
        text = d.ToString();
    }
    sw.Stop();
    sw.ElapsedMilliseconds.Dump("ToString()");

    sw = Stopwatch.StartNew();
    for (int i = 0; i < iterations; i++)
    {
        // 2. how I saw someone do it today
        text = String.Format("{0}", d);
    }
    sw.Stop();
    sw.ElapsedMilliseconds.Dump("Format");
}

---

ToString()
157

Format
264

ToString() looks consistently faster.

EDIT: I should point out, that on my PC 10 million "Format" operations only took 2.2 seconds. This looks very much like a micro-optimization, and unless what you're doing is extremely performance-critical, or iterative - it'd not worry about this too much.

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