How to have placeholder for variable value in java text block

Question

How can I put a variable into java text block?
Like

\"\"\"
{
  ...
  \"someKey\": \"someValue\",
  \"date\": \"${LocalDate.now()}\",
  ...
}
\"\"\"
         


        

Answer 1

You can use %s as placeholder in text blocks

String str = """
{
...
"someKey": "someValue",
"date": %s,
...
}
"""

and replace it using format

String.format(str,LocalDate.now());

From jeps 355 docs

A cleaner alternative is to use String::replace or String::format, as follows:

String code = """
          public void print($type o) {
              System.out.println(Objects.toString(o));
          }
          """.replace("$type", type);

String code = String.format("""
          public void print(%s o) {
              System.out.println(Objects.toString(o));
          }
          """, type);

Another alternative involves the introduction of a new instance method, String::formatted, which could be used as follows:

String source = """
            public void print(%s object) {
                System.out.println(Objects.toString(object));
            }
            """.formatted(type);

Note : But as side note from java-13 docs String.formatted​ is deprecated and suggested to use String.format(this, args).

This method is associated with text blocks, a preview language feature. Text blocks and/or this method may be changed or removed in a future release.