java.util.Formatter

By / 27 May 2025 / 2 minutes of reading

java.util.Formatter is a utility class used to format data (like numbers, strings, etc.) into formatted strings. It behaves similarly to C-style printf formatting and is often used in combination with String.format(), PrintWriter, or directly with console output.

Formatter allows precise control over string formatting, such as padding, alignment, decimal precision, and locale-specific formatting.

Commonly Used Constructors and Methods

Common Formatter Specifiers

Simple Program

import java.util.Formatter;

public class SimpleFormatterExample {
    public static void main(String[] args) {
        Formatter formatter = new Formatter();

        formatter.format("Name: %s%nAge: %d%nSalary: %.2f", "Mahesh", 28, 98765.432);

        System.out.println(formatter.toString());

        formatter.close();
    }
}
/*
Name: Alice
Age: 28
Salary: 98765.43
*/

Problem Statement:

LotusJavaPrince and Mahesh are building a Bank Statement Generator. The system should display user transactions in a neatly formatted tabular format using java.util.Formatter. Each transaction includes Date, Description, and Amount. The table must align properly, use padding, and round amounts to 2 decimal places.

import java.util.Formatter;

class Transaction {
    String date;
    String description;
    double amount;

    public Transaction(String date, String description, double amount) {
        this.date = date;
        this.description = description;
        this.amount = amount;
    }
}

public class BankStatementFormatter {
    public static void main(String[] args) {
        Transaction[] transactions = {
            new Transaction("2025-05-01", "Deposit", 10000.00),
            new Transaction("2025-05-03", "ATM Withdrawal", -1500.50),
            new Transaction("2025-05-05", "Online Purchase", -230.75),
            new Transaction("2025-05-10", "Salary Credit", 25000.00)
        };

        Formatter formatter = new Formatter();

        formatter.format("%-15s %-25s %10s%n", "Date", "Description", "Amount");
        formatter.format("%-15s %-25s %10s%n", "----", "-----------", "------");

        for (Transaction t : transactions) {
            formatter.format("%-15s %-25s %10.2f%n", t.date, t.description, t.amount);
        }

        System.out.println(formatter.toString());
        formatter.close();
    }
}

Output

Date            Description               Amount
----            -----------               ------
2025-05-01      Deposit                  10000.00
2025-05-03      ATM Withdrawal           -1500.50
2025-05-05      Online Purchase           -230.75
2025-05-10      Salary Credit            25000.00Code language: CSS (css)

java.util.Formatter provides powerful string formatting similar to printf.

  • Supports various format specifiers for strings, numbers, and dates.
  • Use cases include reports, logs, invoices, and console output.
  • Can be used directly or with System.out.printf, String.format(), or file writers.

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