Intellij Break On Exception
Riitta Palazzo
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.
Field watchpoints: suspend the program when the specified field is read or written to. This allows you to react to interactions with 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.
Exception breakpoints: suspend the program when Throwable or its subclasses are thrown. They apply globally to the exception condition and do not require a particular source code reference. Unlike stack traces, suspending an application on an exception allows you to examine the surrounding context or data while it is still available.
Caller filters: limit the breakpoint operation depending on the caller of the current method. Select if you need to stop at a breakpoint only when the current method is called (or not called) from a certain method.
Classes and methods are specified using fully qualified names. If a filter is specified through a class name, it points at the class itself and all its subclasses which use its members via inheritance.
You can use patterns that begin or end with the * wildcard to define groups of classes or methods, for example *.Foo or java.*. A filter specified through a pattern points at classes/methods whose fully qualified names match this pattern.
In caller filters, use descriptors for parameters and return types, for example: mypackage.MyObject.addString(Ljava/lang/String;)V. For detailed information on descriptors, refer to the official Oracle documentation.
Select to make the breakpoint work when the specified exception was not caught. This allows you to examine the program state and detect the cause before the program or thread crashes due to unhandled exception.
If it is technically possible to suspend the program at the breakpoint, however there are issues related to it, the debugger sets the breakpoint status to warning. This may happen, for example, when it is impossible to suspend the program at one of the method's implementations.
Use non-suspending logging breakpoints (sometimes referred to as watchpoints in other debuggers) instead of inserting print statements in your code. This provides a more flexible and centralized way of handling debug log messages.
To set a non-suspending logging breakpoint, hold Shift and click the gutter. This will not suspend the program execution and instead log a message like Breakpoint reached at ocean.Whale.main(Whale.java:5). If you want to log some expression that is in front of you in the editor, select it before holding Shift and clicking the gutter.
If you have many breakpoints in your project, you can add descriptions to breakpoints for ease of search. To do this, right-click a breakpoint in the Breakpoints dialog Ctrl+Shift+F8 and select Edit description from the menu. Now when you start typing the breakpoint name, it gets the focus.
Due to JVM design, method references don't provide meaningful information in stack traces, as opposed to lambda expressions. Moreover, it is impossible to set a breakpoint on a method reference. If a method reference reduces traceability where it is critical, consider using a lambda instead.
As exception breakpoints work with Throwable, you can also use them to suspend the program when a subclass of Error is thrown. This is useful for investigating the causes of errors like OutOfMemoryError and StackOverflowError. With an exception breakpoint set up for them, you will be able to look into what happened in the program before it crashes.
A good way to find out if a multi-threaded program is robust in terms of concurrency is to use breakpoints that only suspend one thread when hit. Stopping a single thread may reveal problems in the design of the application, which would not otherwise be evident.
If you do not need to stop in external code, it is recommended to keep this checkbox disabled because it can affect debugger performance, especially if external code throws lots of exceptions. This might be even more noticeable on macOS and Linux, where the .NET debug engine is relatively slow.
Use this option to break on exceptions that are handled neither in user code nor in library code. It is recommended to keep this option enabled because such exception will stop the application process anyway.
In the Breakpoints dialog (Ctrl+Shift+F8 or Run View Breakpoints...) , click and select CLR Exception Breakpoints in case of C# or Visual Basic, or JavaScript Exception Breakpoints in case you debug a script written in JavaScript.
This is a remarkable feature that can work with one small toggle. The crux of the issue is false positives. Code that stops on an exception thrown and caught inside the JVM. This is obviously redundant and happens a lot (e.g. in networking code).
Conditions can apply to any breakpoint type mentioned above. In the video above, I went back to my previous post in this series where I discussed object marking. Object marking effectively lets me define a new global variable label. So I could save Thread.currentThread() as a variable with a new name MyThread. Then I used a condition:
Like other programming style guides, the issues covered span not only aesthetic issues offormatting, but other types of conventions or coding standards as well. However, this documentfocuses primarily on the hard-and-fast rules that we follow universally, andavoids giving advice that isn't clearly enforceable (whether by human or tool).
Example code in this document is non-normative. That is, while the examplesare in Google Style, they may not illustrate the only stylish way to represent thecode. Optional formatting choices made in examples should not be enforced as rules.
Aside from the line terminator sequence, the ASCII horizontal spacecharacter (0x20) is the only whitespace character that appearsanywhere in a source file. This implies that:
The order you choose for the members and initializers of your class can have a great effect onlearnability. However, there's no single correct recipe for how to do it; different classes mayorder their contents in different ways.
What is important is that each class uses some logical order, which itsmaintainer could explain if asked. For example, new methods are not just habitually added to the endof the class, as that would yield "chronological by date added" ordering, which is not a logicalordering.
Methods of a class that share the same name appear in a single contiguous group with no othermembers in between. The same applies to multiple constructors (which always have the same name).This rule applies even when modifiers such as static orprivate differ between the methods.
Exception: In places where these rules allow a single statement ending with a semicolon(;), a block of statements can appear, and the openingbrace of this block is preceded by a line break. Blocks like these are typically introduced tolimit the scope of local variables, for example inside switch statements.
Each time a new block or block-like construct is opened, the indent increases by twospaces. When the block ends, the indent returns to the previous indent level. The indent levelapplies to both code and comments throughout the block. (See the example in Section 4.1.2,Nonempty blocks: K & R Style.)
Java code has a column limit of 100 characters. A "character" means any Unicode code point.Except as noted below, any line that would exceed this limit must be line-wrapped, as explained inSection 4.5, Line-wrapping.
When there are multiple continuation lines, indentation may be varied beyond +4 asdesired. In general, two continuation lines use the same indentation level if and only if theybegin with syntactically parallel elements.
A single blank line may also appear anywhere it improves readability, for example betweenstatements to organize the code into logical subsections. A blank line before the first member orinitializer, or after the last member or initializer of the class, is neither encouraged nordiscouraged.
Optional grouping parentheses are omitted only when author and reviewer agree that there is noreasonable chance the code will be misinterpreted without them, nor would they have made the codeeasier to read. It is not reasonable to assume that every reader has the entire Javaoperator precedence table memorized.
Local variables are not habitually declared at the start of their containingblock or block-like construct. Instead, local variables are declared close to the point they arefirst used (within reason), to minimize their scope. Local variable declarations typically haveinitializers, or are initialized immediately after declaration.
After a switch label, there is a line break, and the indentation level is increased +2, exactlyas if a block were being opened. The following switch label returns to the previous indentationlevel, as if a block had been closed.
Within a switch block, each statement group either terminates abruptly (with abreak,continue,return or thrown exception), or is marked with a commentto indicate that execution will or might continue into the next statement group. Anycomment that communicates the idea of fall-through is sufficient (typically// fall through). This special comment is not required inthe last statement group of the switch block. Example:
Exception: A switch statement for an enum type may omitthe default statement group, if it includesexplicit cases covering all possible values of that type. This enables IDEs or other staticanalysis tools to issue a warning if any cases were missed.
Annotations applying to a class appear immediately after thedocumentation block, and each annotation is listed on a line of its own (that is, one annotationper line). These line breaks do not constitute line-wrapping (Section4.5, Line-wrapping), so the indentation level is notincreased. Example:
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