JShell.Builder (Java SE 26 & JDK 26)
Description: declaration: module: jdk.jshell, package: jdk.jshell, class: JShell, class: Builder
Keywords: jdk.jshell.JShell.Builder class

# Class JShell.Builder

java.lang.Object
jdk.jshell.JShell.Builder

Enclosing class:
  `JShell`

public static class JShell.Builder extends Object
Builder for `JShell` instances. Create custom instances of `JShell` by using the setter methods on this class. After zero or more of these, use the `build()` method to create a `JShell` instance. These can all be chained. For example, setting the remote output and error streams:

        JShell myShell =
          JShell.builder()
            .out(myOutStream)
            .err(myErrStream)
            .build();

If no special set-up is needed, just use `JShell.builder().build()` or the short-cut equivalent `JShell.create()`.

Since:
  9

- ## Method Summary

  Modifier and Type
  Method
  Description
  `JShell`
  `build()`
  Builds a JShell state engine.
  `JShell.Builder`
  `compilerOptions(String... options)`
  Adds compiler options.
  `JShell.Builder`
  `console(JShellConsole console)`
  Sets the console for the running evalution.
  `JShell.Builder`
  `err(PrintStream err)`
  Sets the error output for the running evaluation (it's `System.err`).
  `JShell.Builder`
  `executionEngine(String executionControlSpec)`
  Sets the custom engine for execution.
  `JShell.Builder`
  `executionEngine(ExecutionControlProvider executionControlProvider, Map<String,String> executionControlParameters)`
  Sets the custom engine for execution.
  `JShell.Builder`
  `fileManager(Function<StandardJavaFileManager, StandardJavaFileManager> mapping)`
  Configure the `FileManager` to be used by compilation and source analysis.
  `JShell.Builder`
  `idGenerator(BiFunction<Snippet,Integer,String> generator)`
  Sets the generator of identifying names for Snippets.
  `JShell.Builder`
  `in(InputStream in)`
  Sets the input for the running evaluation (it's `System.in`).
  `JShell.Builder`
  `out(PrintStream out)`
  Sets the output for the running evaluation (it's `System.out`).
  `JShell.Builder`
  `remoteVMOptions(String... options)`
  Sets additional VM options for launching the VM.
  `JShell.Builder`
  `tempVariableNameGenerator(Supplier<String> generator)`
  Sets a generator of temp variable names for `VarSnippet` of `Snippet.SubKind.TEMP_VAR_EXPRESSION_SUBKIND`.

  ### Methods declared in class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`
  Modifier and Type
  Method
  Description
  `protected Object`
  `clone()`
  Creates and returns a copy of this object.
  `boolean`
  `equals(Object obj)`
  Indicates whether some other object is "equal to" this one.
  `protected void`
  `finalize()`
  Deprecated, for removal: This API element is subject to removal in a future version.
  Finalization is deprecated and subject to removal in a future release.
  `final Class<?>`
  `getClass()`
  Returns the runtime class of this `Object`.
  `int`
  `hashCode()`
  Returns a hash code value for this object.
  `final void`
  `notify()`
  Wakes up a single thread that is waiting on this object's monitor.
  `final void`
  `notifyAll()`
  Wakes up all threads that are waiting on this object's monitor.
  `String`
  `toString()`
  Returns a string representation of the object.
  `final void`
  `wait()`
  Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
  `final void`
  `wait(long timeoutMillis)`
  Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
  `final void`
  `wait(long timeoutMillis, int nanos)`
  Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

- ## Method Details

  - ### in

    public JShell.Builder in(InputStream in)
    Sets the input for the running evaluation (it's `System.in`). Note: applications that use `System.in` for snippet or other user input cannot use `System.in` as the input stream for the remote process.

    The `read` method of the `InputStream` may throw the `InterruptedIOException` to signal the user canceled the input. The currently running snippet will be automatically `stopped`.

    The default, if this is not set, is to provide an empty input stream -- `new ByteArrayInputStream(new byte[0])`.

    Parameters:
      `in` - the `InputStream` to be channelled to `System.in` in the remote execution process
    Returns:
      the `Builder` instance (for use in chained initialization)

  - ### out

    public JShell.Builder out(PrintStream out)
    Sets the output for the running evaluation (it's `System.out`). The controlling process and the remote process can share `System.out`.

    The default, if this is not set, is `System.out`.

    Parameters:
      `out` - the `PrintStream` to be channelled to `System.out` in the remote execution process
    Returns:
      the `Builder` instance (for use in chained initialization)

  - ### err

    public JShell.Builder err(PrintStream err)
    Sets the error output for the running evaluation (it's `System.err`). The controlling process and the remote process can share `System.err`.

    The default, if this is not set, is `System.err`.

    Parameters:
      `err` - the `PrintStream` to be channelled to `System.err` in the remote execution process
    Returns:
      the `Builder` instance (for use in chained initialization)

  - ### console

    public JShell.Builder console(JShellConsole console)
    Sets the console for the running evalution.

    The default, if this is not set, is no console (`System.console()` will return `null` while running a snippet).

    Parameters:
      `console` - console to use while a snippet is run
    Returns:
      the `Builder` instance (for use in chained initialization)
    Since:
      21

  - ### tempVariableNameGenerator

    public JShell.Builder tempVariableNameGenerator(Supplier<String> generator)
    Sets a generator of temp variable names for `VarSnippet` of `Snippet.SubKind.TEMP_VAR_EXPRESSION_SUBKIND`.

    Do not use this method unless you have explicit need for it.

    The generator will be used for newly created VarSnippet instances. The name of a variable is queried with `PersistentSnippet.name()`.

    The callback is sent during the processing of the snippet, the JShell state is not stable. No calls whatsoever on the `JShell` instance may be made from the callback.

    The generated name must be unique within active snippets.

    The default behavior (if this is not set or `generator` is null) is to generate the name as a sequential number with a prefixing dollar sign ("$").

    Parameters:
      `generator` - the `Supplier` to generate the temporary variable name string or `null`
    Returns:
      the `Builder` instance (for use in chained initialization)

  - ### idGenerator

    public JShell.Builder idGenerator(BiFunction<Snippet,Integer,String> generator)
    Sets the generator of identifying names for Snippets.

    Do not use this method unless you have explicit need for it.

    The generator will be used for newly created Snippet instances. The identifying name (id) is accessed with `Snippet.id()` and can be seen in the `StackTraceElement.getFileName()` for a `EvalException` and `UnresolvedReferenceException`.

    The inputs to the generator are the `Snippet` and an integer. The integer will be the same for two Snippets which would overwrite one-another, but otherwise is unique.

    The callback is sent during the processing of the snippet and the Snippet and the state as a whole are not stable. No calls to change system state (including Snippet state) should be made. Queries of Snippet may be made except to `Snippet.id()`. No calls on the `JShell` instance may be made from the callback, except to `status(Snippet)`.

    The default behavior (if this is not set or `generator` is null) is to generate the id as the integer converted to a string.

    Parameters:
      `generator` - the `BiFunction` to generate the id string or `null`
    Returns:
      the `Builder` instance (for use in chained initialization)

  - ### remoteVMOptions

    public JShell.Builder remoteVMOptions(String... options)
    Sets additional VM options for launching the VM.
    Parameters:
      `options` - The options for the remote VM
    Returns:
      the `Builder` instance (for use in chained initialization)

  - ### compilerOptions

    public JShell.Builder compilerOptions(String... options)
    Adds compiler options. These additional options will be used on parsing, analysis, and code generation calls to the compiler. Options which interfere with results are not supported and have undefined effects on JShell's operation.
    Parameters:
      `options` - the addition options for compiler invocations
    Returns:
      the `Builder` instance (for use in chained initialization)

  - ### executionEngine

    public JShell.Builder executionEngine(String executionControlSpec)
    Sets the custom engine for execution. Snippet execution will be provided by the `ExecutionControl` instance selected by the specified execution control spec. Use, at most, one of these overloaded `executionEngine` builder methods.
    Parameters:
      `executionControlSpec` - the execution control spec, which is documented in the `jdk.jshell.spi` package documentation.
    Returns:
      the `Builder` instance (for use in chained initialization)

  - ### executionEngine

    public JShell.Builder executionEngine(ExecutionControlProvider executionControlProvider, Map<String,String> executionControlParameters)
    Sets the custom engine for execution. Snippet execution will be provided by the specified `ExecutionControl` instance. Use, at most, one of these overloaded `executionEngine` builder methods.
    Parameters:
      `executionControlProvider` - the provider to supply the execution engine
      `executionControlParameters` - the parameters to the provider, or `null` for default parameters
    Returns:
      the `Builder` instance (for use in chained initialization)

  - ### fileManager

    public JShell.Builder fileManager(Function<StandardJavaFileManager, StandardJavaFileManager> mapping)
    Configure the `FileManager` to be used by compilation and source analysis. If not set or passed null, the compiler's standard file manager will be used (identity mapping). For use in special applications where the compiler's normal file handling needs to be overridden. See the file manager APIs for more information. The file manager input enables forwarding file managers, if this is not needed, the incoming file manager can be ignored (constant function).
    Parameters:
      `mapping` - a function that given the compiler's standard file manager, returns a file manager to use
    Returns:
      the `Builder` instance (for use in chained initialization)

  - ### build

    public JShell build() throws IllegalStateException
    Builds a JShell state engine. This is the entry-point to all JShell functionality. This creates a remote process for execution. It is thus important to close the returned instance.
    Returns:
      the state engine
    Throws:
      `IllegalStateException` - if the `JShell` instance could not be created.