# Continue-As-New - Java SDK

> For the complete documentation index, see [llms.txt](https://docs.temporal.io/llms.txt).
> Any documentation page is available as raw Markdown by appending `.md` to its URL.

> Use Temporal's Continue-As-New in Java to manage large Event Histories by atomically creating new Workflow Executions with the same Workflow Id and fresh parameters.

This page covers the following for Java developers:

- [What is Continue-As-New?](#what)
- [Use Continue-As-New](#how)
- [When is it right to Continue-As-New?](#when)
- [Test Continue-As-New](#how-to-test)

## What is Continue-As-New? 

[Continue-As-New](/workflow-execution/continue-as-new) lets a Workflow Execution close successfully and creates a new Workflow Execution.
You can think of it as a checkpoint when your Workflow gets too long or approaches certain scaling limits.

The new Workflow Execution is in the same [chain](/workflow-execution#workflow-execution-chain); it keeps the same Workflow Id but gets a new Run Id and a fresh Event History.
It also receives your Workflow's usual parameters.

## Use Continue-As-New with the Java SDK 

First, design your Workflow parameters so that you can pass in the "current state" when you Continue-As-New into the next Workflow run.
This state is typically set to `None` for the original caller of the Workflow.

[View the source code](https://github.com/temporalio/samples-java/blob/main/core/src/main/java/io/temporal/samples/safemessagepassing/ClusterManagerWorkflow.java) in the context of the rest of the application code.

```java
class ClusterManagerInput {
  private final Optional<ClusterManagerState> state;
  private final boolean testContinueAsNew;
}

@WorkflowMethod
ClusterManagerResult run(ClusterManagerInput input);

````
The test hook in the above snippet is covered [below](#how-to-test).

Inside your Workflow, call the [`continueAsNew()`](https://javadoc.io/doc/io.temporal/temporal-sdk/latest/io/temporal/workflow/Workflow.html#continueAsNew(io.temporal.workflow.ContinueAsNewOptions,java.lang.Object...)) function with the same type.
This stops the Workflow right away and starts a new one.

[View the source code](https://github.com/temporalio/samples-java/blob/main/core/src/main/java/io/temporal/samples/safemessagepassing/ClusterManagerWorkflowImpl.java) in the context of the rest of the application code.

```java
Workflow.continueAsNew(
  new ClusterManagerInput(Optional.of(state), input.isTestContinueAsNew()));
````

### Considerations for Workflows with Message Handlers 

If you use Updates or Signals, don't call Continue-as-New from the handlers.
Instead, wait for your handlers to finish in your main Workflow before you run `continueAsNew`.

## When is it right to Continue-As-New with the Java SDK? 

Use Continue-as-New when your Workflow might hit [Event History Limits](/workflow-execution/event#event-history).

Temporal tracks your Workflow's progress against these limits to let you know when you should Continue-as-New.
Call `Workflow.getInfo().isContinueAsNewSuggested()` to check if it's time.

## Test Continue-As-New with the Java SDK 

Testing Workflows that naturally Continue-as-New may be time-consuming and resource-intensive.
Instead, add a test hook to check your Workflow's Continue-as-New behavior faster in automated tests.

For example, when `testContinueAsNew == true`, this sample creates a test-only variable called `maxHistoryLength` and sets it to a small value.
A helper method in the Workflow checks it each time it considers using Continue-as-New:

[View the source code](https://github.com/temporalio/samples-java/blob/main/core/src/main/java/io/temporal/samples/safemessagepassing/ClusterManagerWorkflowImpl.java) in the context of the rest of the application code.

```java
private boolean shouldContinueAsNew() {
  if (Workflow.getInfo().isContinueAsNewSuggested()) {
    return true;
  }
  // This is just for ease-of-testing.  In production, we trust temporal to tell us when to
  // continue as new.
  if (maxHistoryLength > 0 && Workflow.getInfo().getHistoryLength() > maxHistoryLength) {
    return true;
  }
  return false;
}
```