Step through the program

Steps over the current line of code and takes you to the next line even if the highlighted line has method calls in it. The implementation of the methods is skipped, and you move straight to the next line of the caller method.

public static void main(String[] args) {
    // the program is suspended here
    count(10);
    System.out.printIn("Count complete!");
}

In the example, line 5 is about to be executed. If you step over, the debugger will move straight to line 6 without visiting the count() method.

public static void main(String[] args) {
    count(10);
    // execution point moves here after Step Over
    System.out.printIn("Count complete!");
}

If there are breakpoints inside the skipped methods, the debugger will stop at them. To skip any breakpoints on the way, use Force step over.

Enters the method to show what happens inside it.

public static void main(String[] args) {
    // the program is suspended here
    count(10);
    System.out.printIn("Count complete!");
}

private static void count(int to) {
    // after Step Into, the program enters the count() method and
    for (int i = 0; i < 10; i++) {
        System.out.println(i);
    }
}

If there are several method calls on the line, IntelliJ IDEA asks you which method to enter. This feature is called Smart step into.

You can configure Smart Step Into to be automatically used every time when there are multiple method calls on the line. Alternatively, it can be invoked only when you expressly do so. To configure this feature, go to Settings | Build, Execution, Deployment | Debugger | Stepping and set the Always do smart step into option as required.

Some methods (for example, methods of standard Java classes like System) are skipped by Step into as you normally might not need to debug them. This list can be fine-tuned on the Build, Execution, Deployment | Debugger | Stepping page of the Settings dialog (CtrlAlt0S) .

Smart step into is helpful when there are several method calls on a line, and you want to be specific about which method to enter. This feature allows you to select the method call you are interested in.

You can configure Smart Step Into to be used instead of the regular Step Into every time there are multiple method calls on the line. This is done in Settings | Build, Execution, Deployment | Debugger | Stepping.

Steps out of the current method and takes you to the caller method.

private static void count(int to) {
    // the program is suspended here
    for (int i = 0; i < 10; i++) {
        System.out.println(i);
    }
}

public static void main(String[] args) {
    count(10);
    // after Step Out, the program exits the count() method
    System.out.printIn("Count complete!");
}

Steps out of the currently executed code block, such as an if statement or a for loop, without exiting the enclosing method.

static void count(int to) {
    for (int i = 0; i < to; i++) {
        // the program is suspended here
        System.out.println(i);
    }
    System.out.println("Complete!");
}

In the example, the action exits the for loop. Note that the loop is executed anyway, and it would print all the numbers to the console as if we had stepped through each iteration.

static void count(int to) {
    for (int i = 0; i < to; i++) {
        System.out.println(i);
    }
    // Step Out of Code Block takes us here
    System.out.println("Complete!");
}

Continues the execution until the position of the caret is reached.

1. Place the caret at the line where you want the program to pause.

2. Select Run to Cursor from the menu or press AltF9.

Also, you can Run to Cursor by hovering over the line and clicking the Run to Cursor icon.

You can configure whether you want Run to Cursor to work on clicking a line number in Settings | Build, Execution, Deployment | Debugger.

In the example, Run to Cursor will continue the execution and stop after the count() method as if there were a breakpoint. If there are actual breakpoints in the skipped code, the program will be suspended upon reaching them.

To skip any breakpoints on the way, use Force run to cursor.

Ultimate

Measure execution time with Run to Cursor

When you use Run to Cursor, it records the execution time for the skipped code fragment and labels each line in the gutter. You can use the labels to navigate to the methods' implementations, whose lines will also be marked with the same type of performance labels.

To turn this feature off, right-click a label and select Disable Recording Time with Run to Cursor.

tip

Run to Cursor is a quick way to measure the performance of a code fragment. If you need to analyze the entire program, consider attaching the profiler.

Steps in the method even if this method is skipped by the regular Step Into.

static void count(int to) {
    for (int i = 0; i < to; i++) {
        // the program is suspended here
            System.out.println(i);
        }
    System.out.println("Complete!");
}

In the example, we jump right into the implementation of the System.out.println() method, while the regular Step Into would proceed to the next iteration of the loop.

public void println(String x) {
    // Force Step Into enters the implementation of PrintStream.println()
    if (getClass() == PrintStream.class) {
        writeln(String.valueOf(x));
    } else {
        synchronized (this) {
            print(x);
            newLine();
        }
    }
}

Continues the execution until the position of the caret is reached. All breakpoints on the way are ignored.

Steps over the current line of code and takes you to the next line even if the current line has method calls in it. If there are breakpoints in the called methods, they are ignored.

Allows you to undo the last frame and restore the previous frame in the stack. This can be useful, for example, if you've mistakenly stepped too far, or want to re-enter a function where you missed a critical spot.

Note that this option only affects local variables and does not restore the overall program state in that it does not revert values for static and instance variables. This may result in an altered program flow.

public static void main(String[] args) {
    count(10);
    System.out.println("Count complete!");
}

private static void count(int to) {
    for (int i = 0; i < to; i++) {
        // the program is suspended here
        System.out.println(i);
    }
}

In the example, dropping the frame returns you to main() as if count has never been executed. There are no static or instance variables, which were affected, however the console output, which has been already produced and can be considered a side effect, stays.

public static void main(String[] args) {
    // Reset Frame returns the execution to the line preceding the last method call
    count(10);
    System.out.println("Count complete!");
}

private static void count(int to) {
    for (int i = 0; i < to; i++) {
        System.out.println(i);
    }
}

note

Reset Frame is not equivalent to going back in time. Keep this in mind when debugging your applications.

IntelliJ IDEA may skip breakpoints under the following circumstances:

• The breakpoint was hit in another thread while stepping or performing Run to Cursor

• The breakpoint was hit within a code block evaluated by a feature such as auto-expressions or watches.

If that happens to breakpoints that are critical for your debugging session, do the following to prevent IntelliJ IDEA from missing them:

• Perform stepping or Run to Cursor from a breakpoint that only pauses the current thread

• Turn off the following features:

  • Auto-expressions in Variables view

  • Alternative view for Collections classes

  • toString() object view

tip

You can configure the debugger notifications on the Appearance & Behavior | Notifications settings page  CtrlAlt0S. For more information, refer to Notifications.

Debugger features consume resources and may impact stepping performance. If the performance is not satisfactory, follow the recommendations provided in this chapter to optimize it.