Java With Us

var (local type inference)

Updated on 2026-04-21 Reviewed by the Java With Us editorial team

var (Java 10+) is a contextual keyword for local variable type inference. Write var x = ... and the compiler figures out x's type from the initialiser. It is not dynamic typing — the type is fixed at compile time, just not written out.

Usage

var name = "Ada";                   // String
var age = 36;                        // int
var list = new ArrayList<String>();  // ArrayList<String>
var now = LocalDateTime.now();       // LocalDateTime

for (var entry : map.entrySet()) {   // Map.Entry<K, V>
    System.out.println(entry.getKey());
}

try (var reader = Files.newBufferedReader(path)) {
    return reader.readLine();
}

Where var is allowed

  • Local variables with an initialiser
  • for loop indices
  • enhanced-for loop variables
  • try-with-resources
  • Lambda parameters (since Java 11, only for adding annotations)

Where var is NOT allowed

  • Field types (private var name; — error)
  • Method parameters or return types
  • Without an initialiser (var x; — error)
  • With a null initialiser (the compiler cannot infer the type)

Style advice

Use var when the type is obvious from the right-hand side (constructors, factory methods, type-name-as-variable-name patterns). Avoid it when the type is not clear from the initialiser — don't force readers to run the compiler in their head.

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