TimeSpan and ConcurrentTimeSpan

/**
 * TimeSpan is not synchronized.
 *
 * If multiple threads access a TimeSpan concurrently, it must be synchronized externally.
 *
 * If multiple threads access a TimeSpan concurrently, ConcurrentTimeSpan are usually recommended.
 *
 * @see ConcurrentTimeSpan
 *
 */
public class TimeSpan {

    private long start;

    public TimeSpan() {
        this(System.currentTimeMillis());
    }

    public TimeSpan(long start) {
        this.start = start;
    }

    public long getSpanAndResetStart() {
        return getSpanAndResetStart(System.currentTimeMillis());
    }

    public long getSpanAndResetStart(long current) {
        try {
            return current - start;
        } finally {
            start = current;
        }
    }

    public long getSpan() {
        return getSpan(System.currentTimeMillis());
    }

    public long getSpan(long current) {
        return current - start;
    }

    public long getStart() {
        return start;
    }

    public void setStart() {
        setStart(System.currentTimeMillis());
    }

    public void setStart(long start) {
        this.start = start;
    }

}

import java.util.concurrent.atomic.AtomicLong;

/**
 * ConcurrentTimeSpan are synchronized.
 *
 * @see TimeSpan
 *
 */
public class ConcurrentTimeSpan {

    private final AtomicLong start;

    public ConcurrentTimeSpan() {
        this(System.currentTimeMillis());
    }

    public ConcurrentTimeSpan(long start) {
        this.start = new AtomicLong(start);
    }

    public long getSpanAndResetStart() {
        return getSpanAndResetStart(System.currentTimeMillis());
    }

    public long getSpanAndResetStart(long current) {
        return current - start.getAndSet(current);
    }

    public long getSpan() {
        return getSpan(System.currentTimeMillis());
    }

    public long getSpan(long current) {
        return current - start.get();
    }

    public long getStart() {
        return start.get();
    }

    public void setStart() {
        setStart(System.currentTimeMillis());
    }

    public void setStart(long start) {
        this.start.set(start);
    }

}