How to Use Placeholders for Variable Values in Java Text Blocks?

Question

How can I include variable values in Java text blocks using placeholders?

String name = "World";
String greeting = """Hello, %s!""".formatted(name);  // Java 15+ 
System.out.println(greeting); // Output: Hello, World!

Answer

In Java, a text block is a multi-line string literal that allows for easy formatting and readability. To dynamically include variable values within a text block, placeholders are often required. This can be achieved using the `String.format()` method or the new `String.formatted()` method introduced in Java 15.

String name = "World";
String greeting = String.format("""Hello, %s!""", name);
System.out.println(greeting); // Output: Hello, World!

Causes

  • Text blocks define static strings but do not directly support variable interpolation.
  • Using placeholders requires additional formatting methods.

Solutions

  • Utilize `String.format()` or `.formatted()` methods to substitute variable values into the text block.
  • For example, use `String greeting = String.format("Hello, %s!", name);` to include the variable `name` within the text block.

Common Mistakes

Mistake: Using text blocks expecting automatic variable substitution.

Solution: Always use formatting methods like `String.format()` or `.formatted()` to insert variable values.

Mistake: Not handling null values in placeholders.

Solution: Ensure that variables used in placeholders are initialized to avoid NullPointerExceptions.

Helpers

  • Java text block
  • placeholders in Java
  • Java string formatting
  • Java 15 features
  • how to use text blocks in Java

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