Is there a way to interpolate strings in Java?

Question

I’m starting in Java and found the path to concatenate String and variables very tiring.

In Javascript, we can use `string ${variavel}`; in Python, 'string {}'.format(variavel) or f'string {variavel}' etc..

I wonder if there is something like this in Java or some way to simplify the concatenation that is not so:

"string" + variavel + "string"

Answer 1

In Java you have the class Formatter for this. And in fact it is more suitable in various situations. There are other options, the class itself string has a.

I just wouldn’t say she’s less tiresome. Anyway if this is tiring I would suggest thinking about working with something else, you have to do what is most suitable, no matter what work it takes. And I think formatting is more work than concatenating (not that it changes much). But concatenating is usually less advantageous than formatting, although in the specific context it may not be (the implementation may be optimized in some scenarios and the compiler makes it equal to concatenation). Formatting tends to be more laborious.

Programming is understanding what you’re doing and choosing the best mechanism for the context, not the easiest to type, or the cutest looking one.

Depending on where to use it has a variety of methods that use the Formatter for you, example is if printing since some printing methods already have internal formatting. Here the work of formatting gets reduced, but can only use in console scenario or other that has an internal formatting mechanism where the text will be used.

Answer 2

In Java, one option is to use printf:

String nome = "Fulano";
int idade = 20;

System.out.printf("%s tem %d anos\n", nome, idade); // Fulano tem 20 anos

The format string syntax is inspired by C, so you should indicate the type of each information being displayed (in the above case, %s indicates a string and %d indicates an integer). View documentation for more details.

It is worth remembering that printf is more than just concatenating, since you can choose alignment and fill options (for example, printing the text aligned to the right, occupying 20 positions, or printing the number with zeros to the left, including determining the quantity, etc.). For example, %05d would cause the number above to be printed as 00020.

Finally, to see all the options, see the aforementioned documentation. It is a more powerful mechanism than simple concatenation, so you should choose the one that is most suitable for your case (do not use as a criterion "is shorter" or "tires less", use what makes the most sense for what you need to do).

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But if instead of printing, you want to generate a string with the result of concatenation/formatting, then you can use String.format, whose syntax is similar:

String mensagem = String.format("%s tem %d anos", nome, idade);

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Another option is to use java.text.MessageFormat, whose syntax resembles a little more the format python:

String mensagem = MessageFormat.format("{0} tem {1} anos", nome, idade);

But this class has some interesting options, such as setting the text to singular and plural:

String mensagem = MessageFormat.format("{0} tem {1} {1,choice,1#ano|1<anos}", nome, idade);

So if age is 1, the message will be Fulano tem 1 ano, but if it’s different from 1 (for example, 20), there will be Fulano tem 20 anos. Again, be sure to see on documentation all available options.