JAVA / STRINGS

Text blocks — what changed in Java 15

Easy

Java 15 made text blocks standard: a multi-line string between """ delimiters. The compiler strips the shared indentation and trailing spaces and turns line endings into \n. No escaped quotes or + chains. The result is an ordinary String.

How it works

Syntax. Opening """ must be followed by a line break; content starts on the next line. The closing """ can sit at the end of the last line or on its own line.
History. Preview in Java 13 and 14, standard (final) in Java 15 (JEP 378).
What the compiler does, in order:
- Normalizes every line ending (\r\n, \r) to \n, so the value doesn't depend on the OS that saved the file.
- Removes incidental indentation: the smallest leading whitespace among the non-blank lines (and the closing delimiter's line) is stripped from every line.
- Strips trailing spaces from each line.
- Only then interprets escape sequences.
New escapes. \ at the end of a line joins it with the next (no \n). \s is a single space that survives the trailing-space strip.
Same type. The result is a compile-time constant String, interned like any literal. Java 15 also added String.formatted(...), handy for filling in values.

Example

// Before: escapes and concatenation
String oldJson = "{\n" +
                 "  \"sku\": \"%s\",\n" +
                 "  \"qty\": %d\n" +
                 "}\n";

// After: what you see is what you get
String json = """
        {
          "sku": "%s",
          "qty": %d
        }
        """.formatted("KB-104", 3);

// Line-join and a kept trailing space
String sql = """
        SELECT id, name \
        FROM customers \
        WHERE active = true""";   // one line, no trailing \n

String padded = """
        name:\s
        """;                       // "name: \n"

Edge cases

The closing delimiter's position controls indentation. Move it left of the content and the extra spaces become part of the string.
Closing """ on its own line adds a final \n; closing on the last content line doesn't.
A single " or a pair "" needs no escaping inside. Three in a row do: write \""".
Mixing tabs and spaces in indentation is legal but confusing, since each counts as one whitespace character.

Common mistakes

Putting content on the same line as the opening """. That's a compile error.
Expecting text blocks to interpolate variables like ${name}. Java has no string interpolation; use formatted or +.
Being surprised by a trailing \n in tests that compare against a literal without one.

Likely follow-up

"Are text blocks slower or different at runtime?" No. All processing happens at compile time. The bytecode holds an ordinary string constant, the same as a regular literal with the escapes written out.

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