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Generate Random Timestamps in Java

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[ Code Example - Quick Summary ]

Language: Java

What: Generate random Unix timestamps in Java using System.currentTimeMillis() and Random. Covers current time, past/future timestamps, and formatting for testing.

Try it: Use our interactive Timestamps generator or integrate this code into your Java application.

Generate random Unix timestamps in Java using System.currentTimeMillis() and Random. Covers current time, past/future timestamps, and formatting for testing. Looking for other languages? Check our code examples in PHP , JavaScript , Python , C# , C++ , Ruby and Go or use our interactive web generator.

Java Code Example

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.ThreadLocalRandom;

public class TimestampGenerator {
    private static final Random random = new Random();

    // Generate current Unix timestamp (seconds)
    public static long currentTimestamp() {
        return Instant.now().getEpochSecond();
    }

    // Generate current Unix timestamp (milliseconds)
    public static long currentTimestampMillis() {
        return System.currentTimeMillis();
    }

    // Generate random timestamp between two dates
    public static long randomTimestamp(String startDate, String endDate) {
        long start = LocalDateTime.parse(startDate + "T00:00:00")
            .atZone(ZoneId.systemDefault()).toEpochSecond();
        long end = LocalDateTime.parse(endDate + "T23:59:59")
            .atZone(ZoneId.systemDefault()).toEpochSecond();
        return ThreadLocalRandom.current().nextLong(start, end + 1);
    }

    // Generate random past timestamp (within N days)
    public static long randomPastTimestamp(int daysAgo) {
        long now = Instant.now().getEpochSecond();
        long seconds = daysAgo * 86400L;
        return now - ThreadLocalRandom.current().nextLong(0, seconds);
    }

    // Generate random future timestamp (within N days)
    public static long randomFutureTimestamp(int daysAhead) {
        long now = Instant.now().getEpochSecond();
        long seconds = daysAhead * 86400L;
        return now + ThreadLocalRandom.current().nextLong(0, seconds);
    }

    // Convert timestamp to readable format
    public static String formatTimestamp(long timestamp) {
        return LocalDateTime.ofInstant(
            Instant.ofEpochSecond(timestamp),
            ZoneId.systemDefault()
        ).format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
    }

    // Generate multiple random timestamps
    public static List<Long> generateTimestamps(int count, String startDate, String endDate) {
        List<Long> timestamps = new ArrayList<>();
        for (int i = 0; i < count; i++) {
            timestamps.add(randomTimestamp(startDate, endDate));
        }
        return timestamps;
    }

    public static void main(String[] args) {
        System.out.println("Current: " + currentTimestamp());
        System.out.println("Random: " + randomTimestamp("2023-01-01", "2024-12-31"));
        long past = randomPastTimestamp(30);
        System.out.println("Past: " + past + " (" + formatTimestamp(past) + ")");
        long future = randomFutureTimestamp(30);
        System.out.println("Future: " + future + " (" + formatTimestamp(future) + ")");
        System.out.println("Batch: " + generateTimestamps(3, "2023-01-01", "2024-12-31"));
    }
}

[EXPLANATION]

Java Instant.now().getEpochSecond() returns current Unix timestamp in seconds. System.currentTimeMillis() returns milliseconds since epoch. ThreadLocalRandom is thread-safe for concurrent generation. LocalDateTime.parse() parses dates, atZone() adds timezone. DateTimeFormatter formats output. Java 8+ time API (java.time) is preferred over legacy Date class.

Expected Output

Current: 1703001234
Random: 1698765432
Past: 1700445678 (2023-11-19 14:27:58)
Future: 1706123456 (2024-01-24 18:10:56)
Batch: [1680123456, 1685432100, 1692345678]