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Language Beginner

Unnamed variables with _

Use _ to signal intent when a variable is intentionally unused.

Code Comparison

✕ Java 8

try {
    parse(input);
} catch (Exception ignored) {
    log("parse failed");
}
map.forEach((key, value) -> {
    process(value); // key unused
});

✓ Java 22+

try {
    parse(input);
} catch (Exception _) {
    log("parse failed");
}
map.forEach((_, value) -> {
    process(value);
});

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Why the modern way wins

📢

Clear intent

_ explicitly says 'this value is not needed here'.

🔇

No warnings

IDEs and linters won't flag intentionally unused variables.

🧹

Cleaner lambdas

Multi-param lambdas are cleaner when you only need some params.

Old Approach

Unused Variable

Modern Approach

_ Placeholder

Since JDK

Difficulty

Beginner

JDK Support

Unnamed variables with _

Available

Finalized in JDK 22 (JEP 456, March 2024).

How it works

Unnamed variables communicate to readers and tools that a value is deliberately ignored. No more 'ignored' or 'unused' naming conventions, no more IDE warnings.

Type inference with var

Java 8

Map<String, List<Integer>> map =
    new HashMap<String, List<Integer>>();
for (Map.Entry<String, List<Integer>> e
    : map.entrySet()) {
    // verbose type noise
}

Java 10+

var map = new HashMap<String, List<Integer>>();
for (var entry : map.entrySet()) {
    // clean and readable
}

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JDK 10+ →

Language Beginner

Text blocks for multiline strings

Java 8

String json = "{\n" +
    "  \"name\": \"Duke\",\n" +
    "  \"age\": 30\n" +
    "}";

Java 15+

String json = """
    {
      "name": "Duke",
      "age": 30
    }""";

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JDK 15+ →

Language Beginner

Switch expressions

Java 8

String msg;
switch (day) {
    case MONDAY:
        msg = "Start";
        break;
    case FRIDAY:
        msg = "End";
        break;
    default:
        msg = "Mid";
}

Java 14+

String msg = switch (day) {
    case MONDAY  -> "Start";
    case FRIDAY  -> "End";
    default      -> "Mid";
};

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JDK 14+ →