IntelliJ IDEA 2019.2 Help

Breakpoints

Breakpoints are source code markers that let you suspend program execution at a specific point and examine its behavior.

Once set, a breakpoint remains in your project until you remove it explicitly (except for temporary line breakpoints). If a file with breakpoints was modified externally, for example, updated through a VCS or changed in an external editor, and the line numbers have changed, breakpoints will be moved accordingly. Note that IntelliJ IDEA must be running when such changes are made, otherwise they will pass unnoticed.

Line breakpoints

Line breakpoints can be set on executable lines of code. Thread execution is suspended before the line with such breakpoint, and IntelliJ IDEA displays the stack frames on that thread's stack.

Set a line breakpoint

  1. Place the caret at an executable line of code where you want to set a breakpoint.

    If you want to set a breakpoint in the default class constructor, set it on the first line of this class, since the default constructor is mapped to it.

  2. Click the left gutter next to that line or press Ctrl+F8.

    To set a temporary line breakpoint, press Ctrl+Shift+Alt+F8. It will be removed from your project right after it has been hit.

For lambda expressions, you can set multiple breakpoints within a single line. Click the left gutter and select methods where you want to set a breakpoint from the list:

lambda breakpoints

Remove a line breakpoint

  • Click the breakpoint icon in the left gutter.

To avoid accidentally removing a breakpoint and losing its parameters, you can choose to remove breakpoints by dragging them to the editor, or by clicking the middle mouse button: in the Settings/Preferences dialog Ctrl+Alt+S go to Build, Execution, Deployment | Debugger and select Drag to the editor or click with middle mouse button. Clicking a breakpoint will then toggle its state (enabled/disabled).

Method breakpoints

Method breakpoints act in response to the program entering or exiting a particular method. They let you follow the program flow at the method level, and check entry and exit conditions.

Set a method breakpoint

  • Click the left gutter next to the line with the method declaration.

By default, IntelliJ IDEA sets an emulated method breakpoint, which is a combination of line breakpoints set at first statements of all implementing or overriding methods. Such emulated breakpoints do not impact the debugged application performance, while "true" method breakpoints slow the debugger dramatically due to the JVM design.

Emulated method breakpoints do not work for native methods and classes without the line number information. If this is your case, right-click a method breakpoint and deselect the Emulated option:

method breakpoint properties

Remove a method breakpoint

  • Click the method breakpoint icon the Method breakpoint icon in the left gutter.

To avoid accidentally removing a breakpoint and losing its parameters, you can choose to remove breakpoints by dragging them to the editor, or by clicking the middle mouse button: in the Settings/Preferences dialog Ctrl+Alt+S go to Build, Execution, Deployment | Debugger and select Drag to the editor or click with middle mouse button. Clicking a breakpoint will then toggle its state (enabled/disabled).

Exception breakpoints

Exception breakpoints are triggered when the specified exception is thrown. They apply globally to the exception condition and do not require a particular source code reference.

Set an exception breakpoint

  1. Press Ctrl+Shift+F8 or select Run | View Breakpoints from the main menu.

  2. In the Breakpoints dialog, press Alt+Insert or click the Add button, and select Java Exception Breakpoint or JavaScript Exception Breakpoint.

  3. In the Enter Exception Class dialog, specify an exception class from the library or from your project.

Remove an exception breakpoint

  1. Press Ctrl+Shift+F8 or select Run | View Breakpoints from the main menu.

  2. In the Breakpoints dialog, select the breakpoint you want to delete under Java Exception Breakpoints and click the Remove button or press Alt+Delete.

Field watchpoints

Field watchpoints allow you to react to modifications of specific instance variables. For example, if at the end of a complicated process you are ending up with an obviously wrong value on one of your fields, setting a field watchpoint may help determine the origin of the fault.

Set a field watchpoint

  1. During a debugging session, open the Variables view.

  2. Right-click a field and select Add Field Watchpoint from the context menu.

You can also open a class in the editor, locate the field that you want to create a watchpoint for, and Alt+click the left gutter at the field declaration line.

Remove a field watchpoint

  1. Press Ctrl+Shift+F8 or select Run | View Breakpoints from the main menu.

  2. In the Breakpoints dialog, select the breakpoint you want to delete under Field Watchpoints and click the Remove button or press N/A.

Breakpoints properties

Depending on the breakpoint type, you can configure additional properties, such as:

  • actions to be performed when hitting a breakpoint

  • a suspend policy that defines whether the application must be suspended when a breakpoint is hit

  • dependencies on other breakpoints

  • conditions that define when a breakpoint must be hit

To edit breakpoint properties press Ctrl+Shift+F8, or right-click a breakpoint in the editor gutter.

Option

Description

Breakpoint type

Enabled

Clear to temporarily disable a breakpoint without removing it from the project. Disabled breakpoints will be skipped during the debugging process.

Line
Exception
Method
Field Watchpoint

Suspend

Select to pause the program execution when a breakpoint is hit. Suspending an application is useful if you need to obtain logging information or calculate an expression at a certain point without interrupting the program. If you need to create a master breakpoint that will trigger dependent breakpoints when hit, choose not to suspend the program at that breakpoint.

Choose the suspend policy:

  • All: all threads will be suspended

  • Thread: only the thread containing this breakpoint will be suspended. If you want the Thread policy to be used as the default one, click the Make default button.

Line
Exception
Method
Field Watchpoint

Condition

Select to specify a condition for hitting a breakpoint. A condition is a Java Boolean expression including a method returning true or false, for example, str1.equals(str2).

This expression must be valid at the line where the breakpoint is set, and it is evaluated each time the breakpoint is hit. If the evaluation result is true, the selected actions are performed.

You can enter multi-line expressions, for example:

if (myvar == expectedVariable) { System.out.println (myvar); anotherVariable = true; } return true;

Line
Exception
Method
Field Watchpoint

Log

Select if you want to log the following events to console:

  • "Breakpoint hit" message: a log message will be displayed in the console output when the breakpoint is hit.

  • Stack trace: the breakpoint's stack trace will be printed to the console when it's hit.

    This is useful if you want to check what paths have led to this point without interrupting the program's execution.

Line
Exception
Method
Field Watchpoint

Evaluate and log

Select to evaluate an expression when the breakpoint is hit, and show the result in the console output.

Line
Exception
Method
Field Watchpoint

Remove once hit

Select to remove the breakpoint from your project right after it has been hit.

Line
Exception
Method

Disable until breakpoint is hit

Select the breakpoint that will trigger the current breakpoint. Until that breakpoint is hit, the current breakpoint will be disabled. You can also select if you wish to disable it again or leave it enabled once it has been hit.

Line
Exception
Method
Field Watchpoint

Catch class filters

Select to filter out classes where exceptions will be caught. Either type in the filters, or click browse and configure filters in the Class Filters dialog.

You can specify class names or class patterns (strings with the * wildcard). If a filter is specified through a class name, it points at the class itself and all its subclasses. A filter specified through a class pattern points at classes whose fully qualified names match this pattern.

Syntax:

  • use spaces to separate class names and patterns

  • to exclude a class, type - before the class name

For example, -java.* -sun.* means that the breakpoint must not be triggered for exceptions caught inside the java and sun packages.

Exception

Instance filters

Select to limit breakpoint hits with particular object instances. Enter instance IDs separated by spaces, or click browse and add them in the Instance Filters dialog.

Line
Method
Exception
Field Watchpoint

Class filters

Select to filter classes where the breakpoint must be hit. Either type in the filters, or click browse and configure filters in the Class Filters dialog.

You can specify class names or class patterns (strings with the * wildcard). If a filter is specified through a class name, it points at the class itself and all its subclasses. A filter specified through a class pattern points at classes whose fully qualified names match this pattern.

Syntax:

  • use spaces to separate class names and patterns

  • to exclude a class, type - before the class name

For example, package1.Class1 *s2 -package3.Class3 means that the breakpoint must be triggered in the package1.Class1 class and all its subclasses, and in classes whose fully qualified name ends in s2; it must not be triggered in the package3.Class3 class and its subclasses.

Line
Exception
Method
Field Watchpoint

Pass count

Select if you need a breakpoint to be triggered only after it has been hit a certain number of times. This is useful for debugging loops or methods called several times.

Line
Exception
Method
Field Watchpoint

Caller filters

Select if you need to stop at a breakpoint only when it is called (or NOT called) from a certain method. Either type in the caller methods, or click open and configure filters in the Caller Filters dialog.

You can specify method names or method patterns (strings with the * wildcard).

Syntax:

  • use spaces to separate methods and patterns

  • to exclude a method, type - before the class name

Line
Exception
Method
Field Watchpoint

Watch

Field access

Select to trigger the breakpoint each time the field is accessed.

Field watchpoint

Field modification

Select to trigger the breakpoint only when the field is modified.

Field watchpoint

Emulated

This option is set by default when you create a method breakpoint. Instead of using a slow method breakpoint, IntelliJ IDEA sets a combination of line breakpoints at first statements of all implementing or overriding methods that emulate a method breakpoint.

We only recommend to deselect this option if you are debugging a remote code (as emulated breakpoints can be very slow to set), or if you need to set a breakpoint at methods without the line number information.

Method

Method entry

Select to trigger the breakpoint each time the method is entered.

Method

Method exit

Select to trigger the breakpoint each time the method is exited.

Method

Notifications

Caught exception

Select to be notified when you've hit a breakpoint on a caught exception.

Exception

Uncaught exception

Select to be notified when you've hit a breakpoint on an uncaught exception.

Exception

Productivity tips

Quick access to most common settings

Right-click a breakpoint in the editor gutter to quickly disable or suspend it, or set a condition.

Breakpoints intentions

You can get access to the most common breakpoint actions and filters through intention actions (Alt+Enter).

breakpoint intentions

When a breakpoint is hit, more intention actions are available.

Group breakpoints

You can organize breakpoints into groups, for example, if you need to mark out breakpoints for a specific problem.

In the Breakpoints dialog Ctrl+Shift+F8, select a breakpoint you want to place in a group and choose Move to group | <group_name>/Create new from the context menu.

Move breakpoints

To move a line breakpoint, drag it to the target line.

Copy breakpoints

To copy a breakpoint, press Ctrl and drag it to the target line.

Disable breakpoints

To temporarily disable a breakpoint without removing it from the project, hold down the Alt key and click the breakpoint icon in gutter.

Quick search

If you have many breakpoints in your project, you can add short descriptions to them to search for them easily: right-click a breakpoint in the Breakpoints dialog Ctrl+Shift+F8 and select Edit description from the context menu. Now when you start typing a breakpoint's name, it gets the focus.

Jump to source

To jump from the Breakpoints dialog to the line of code where the selected breakpoint is set, press F4.

Last modified: 19 August 2019

See Also