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How to Convert int to String in Java

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

Three idiomatic ways to convert an int to a String in Java: String.valueOf(n), Integer.toString(n), and string concatenation "" + n. All produce identical results for normal integers.

String.valueOf() — recommended

int n = 42;
String s = String.valueOf(n);  // "42"

Works for any primitive type (long, double, boolean, etc.) and for Object references (handles null by returning "null"). Most readable and explicit.

Integer.toString()

int n = 42;
String s = Integer.toString(n);         // "42"
String binary = Integer.toString(n, 2); // "101010" (base-2)
String hex    = Integer.toString(n, 16);// "2a"

Use the two-argument form when you need a different radix.

Concatenation — quick but opaque

int n = 42;
String s = "" + n;        // "42"
String s2 = n + " items"; // "42 items"

Works but is less clear about intent. Fine for quick conversions or when you are building a string anyway. The compiler optimises it to StringBuilder under the hood.

String.format() — for formatted output

int price = 9;
String s = String.format("%05d", price);  // "00009" (zero-padded, width 5)
String t = String.format("%,d", 1000000); // "1,000,000" (locale-aware grouping)

Formatted strings (Java 15+ text blocks / Java 21 string templates preview)

int count = 3;
String msg = "You have %d messages".formatted(count); // "You have 3 messages"

Converting Integer (boxed) to String

Integer boxed = 42;
String s = boxed.toString();       // "42"
String s2 = String.valueOf(boxed); // "42"

Both handle the unboxing automatically. String.valueOf(null) returns "null"; calling .toString() on a null Integer throws a NullPointerException.

Performance note

All three conversion methods are fast and O(1) in terms of string length (an int has at most 11 characters including sign). Do not optimise this — pick the most readable form.

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