IntelliJ IDEA enables you to evaluate an arbitrary expression in the context of a stack frame currently selected in the Frame pane of the Debug window. So doing, the following modes are available:
- Expression Mode for evaluating single-line expressions.
- Code Fragment Mode for evaluating short code portions introducing them in the Statements to evaluate text field. Supported constructs are declarations, assignments, loops and if/else.
Besides that, IntelliJ IDEA provides a way to quickly evaluate in the editor an expression at caret or a selection.
While using the Expression Evaluation feature, be aware of the following:
- A method can be invoked within the Expression Evaluation dialog only if the debugger has stopped at a breakpoint, but has not been paused.
- Expression Evaluation can be only "single-level". In other words, if IntelliJ IDEA stops at a breakpoint within a method called from the Expression Evaluation, you cannot use the Expression Evaluation feature again.
- If a method invoked within the Expression Evaluation has a breakpoint inside its body, this breakpoint will be ignored.
- In the Frames pane, select the thread where you want an expression to be evaluated.
Evaluate Expression in one of the following ways:
- On the main menu, choose
- On the context menu of the editor, choose
- Click on the stepping toolbar of the Debug tool window.
- Select the desired mode of evaluation. If you want to evaluate a code fragment, click the Code Fragment Mode button.
Depending on the mode selected, type the expression or statements to evaluate in the text field.
If you have assigned a label to a variable, object, or watch, you can reference it by this label as if it were a local variable <label-name>_DebugLabel defined in the same context where the expression is evaluated. IntelliJ IDEA also displays this label in the completion suggestion list.
If the specified expression cannot be evaluated, the possible reason will be briefly described in the
Result pane of the dialog box.
During the debugger session, the value of any expression at caret is shown at the tooltip every time you hover your mouse pointer over it. If an expression contains children, clicking expands the node and displays all children.
However, Quick evaluate expression helps you view the expression value using the keyboard only.
- Place the caret at the desired location, or select an expression to be evaluated.
or or or or or or or or or or or . The tooltip with the expression value appears under
the selected expression.