chinabugotech/hutool · error · IllegalStateException

Can't start StopWatch: it's already running

Error message

Can't start StopWatch: it's already running

What it means

Error "Can't start StopWatch: it's already running" thrown in chinabugotech/hutool.

Source

Thrown at hutool-core/src/main/java/cn/hutool/core/date/StopWatch.java:157

	/**
	 * 开始默认的新任务
	 *
	 * @throws IllegalStateException 前一个任务没有结束
	 */
	public void start() throws IllegalStateException {
		start(StrUtil.EMPTY);
	}

	/**
	 * 开始指定名称的新任务
	 *
	 * @param taskName 新开始的任务名称
	 * @throws IllegalStateException 前一个任务没有结束
	 */
	public void start(String taskName) throws IllegalStateException {
		if (null != this.currentTaskName) {
			throw new IllegalStateException("Can't start StopWatch: it's already running");
		}
		this.currentTaskName = taskName;
		this.startTimeNanos = System.nanoTime();
	}

	/**
	 * 停止当前任务
	 *
	 * @throws IllegalStateException 任务没有开始
	 */
	public void stop() throws IllegalStateException {
		if (null == this.currentTaskName) {
			throw new IllegalStateException("Can't stop StopWatch: it's not running");
		}

		final long lastTime = System.nanoTime() - this.startTimeNanos;
		final long safeLastTime = Math.max(0, lastTime);
		this.totalTimeNanos += safeLastTime;

View on GitHub (pinned to 8870454b2a)

Solutions

1. Call stop() before calling start() again on the same StopWatch.
2. Create a new StopWatch instance for each measurement.

When it happens

Trigger: Thrown at hutool-core/src/main/java/cn/hutool/core/date/StopWatch.java:157 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of chinabugotech/hutool@8870454b2a (2026-08-14). Data as JSON: /api/errors/ba69ffd90e823ac8. Report an issue: GitHub.