Java:
Interpolating a string
How to:
Java introduced String.format() for interpolation:
public class StringInterpolationExample {
public static void main(String[] args) {
String user = "Alice";
int points = 1337;
String greeting = String.format("Hi, %s! You have %d points.", user, points);
System.out.println(greeting);
}
}Sample output:
Hi, Alice! You have 1337 points.For more modern interpolation since Java 15, we use text blocks and formatted():
public class ModernStringInterpolationExample {
public static void main(String[] args) {
String user = "Bob";
double accountBalance = 1234.56;
String message = """
Dear %s,
Your current balance is $%.2f.
""".formatted(user, accountBalance);
System.out.println(message);
}
}Sample output:
Dear Bob,
Your current balance is $1234.56.Deep Dive
Before interpolation, Java relied on concatenation: String greeting = "Hello, " + user + "!";. Cumbersome and error-prone, especially as strings got complex.
Historically, languages like Perl and PHP had interpolation. Java caught up much later. String.format() and PrintStream.printf() offer similar functionality, using format specifiers that tell Java how to handle variables.
Alternatives? Besides String.format(), we’ve got MessageFormat and StringBuilder, but they’re not as slick for basic interpolation. Since Java 15, text blocks simplified multi-line strings and added formatted() to streamline interpolation directly in place.
Implementation-wise, String.format() uses Formatter, a robust engine with many formatting options. But beware, complex strings can tank your app’s performance if you’re not careful.