String.format

Learn formatting with String.format().

String.format

String.format fills a template with values. %s for String, %d for integer, %.2f for decimal.

String name = "Alex";
int age = 28;
String result = String.format("Hello %s, age %d", name, age);
// "Hello Alex, age 28"

%.2f rounds the decimal to two digits: String.format("Price: %.2f", 9.999) → "Price: 10.00".

The template must match the number of variables; otherwise an exception is thrown.

Exercise Use String.format

Write a Main class with a main method. Assign "Alex" to String name and 28 to int age. Assign String.format("Hello %s, age %d", name, age) to String result. Print result with println.

Show example solution

public class Main {
    public static void main(String[] args) {
        String name = "Alex";
        int age = 28;
        String result = String.format("Hello %s, age %d", name, age);
        System.out.println(result);
    }
}

Common placeholders

The most common placeholders:

%s: String
%d: integer (int, long)
%f: decimal (double, float)
%.2f: two decimal digits
%n: platform-correct newline
%b: boolean

For width use %5d (5 chars right-aligned), %-5d (left-aligned). This is useful for tabular output.

Test yourself

Match the placeholders

%s

String
%d

Integer
%.2f

Decimal
%n

Newline

Complete the placeholder

String s = String.format("Age: ____", 28);

Show answer

String s = String.format("Age: %d", 28);

Which is the placeholder for decimals?
- %f
- %d
- %s
- %n
Show answer

%f — %f is the decimal placeholder.

Next lesson: Summary - String basics

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