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Q&A How to log first n lines of a stack trace in Java?

It's not clear where this stack trace comes from (either from an exception or the current thread), but it doesn't matter, the way to do it is the same. Both Exception's and Thread's have the getSt...

posted 2mo ago by hkotsubo‭ · edited 2mo ago by hkotsubo‭

Answer

#2: Post edited by

hkotsubo‭ · 2024-02-29T15:04:56Z (2 months ago)

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It's not clear where this stack trace comes from (either from an exception or the current thread), but it doesn't matter, the way to do it is the same.
Both `Exception`'s and `Thread`'s have the `getStackTrace()` method. For the current thread, you can use `Thread.currentThread().getStackTrace()`, but you can call the method for any other thread as well.
In either case, the `getStackTrace` method will return an array of `StackTraceElement`'s. Just remind that, for threads, it'll return an a zero-length array if the thread has not started, has started but has not yet been scheduled to run by the system, or has terminated.
Anyway, once you have the array, it's very straighforward to log the first N lines:
```java
int limit = 5; // number of elements to log
// Get the stack trace from an exception
// or use Thread.currentThread().getStackTrace() to get from the current thread
// or simply thread.getStackTrace() to get from any other thread
StackTraceElement[] elements = exception.getStackTrace();
// just in case the array has fewer elements than the limit
int len = Math.min(elements.length, limit);
for (int i = 0; i < len; i++) {
log.error(elements[i].toString());
}
```

It's not clear where this stack trace comes from (either from an exception or the current thread), but it doesn't matter, the way to do it is the same.
Both `Exception`'s and `Thread`'s have the `getStackTrace()` method. For the current thread, you can use `Thread.currentThread().getStackTrace()`, but you can call the method for any other thread as well.
In either case, the `getStackTrace` method will return an array of `StackTraceElement`'s. Just remind that, for threads, it'll return a zero-length array if the thread has not started, has started but has not yet been scheduled to run by the system, or has terminated.
Anyway, once you have the array, it's very straighforward to log the first N lines:
```java
int limit = 5; // number of elements to log
// Get the stack trace from an exception
// or use Thread.currentThread().getStackTrace() to get from the current thread
// or simply thread.getStackTrace() to get from any other thread
StackTraceElement[] elements = exception.getStackTrace();
// just in case the array has fewer elements than the limit
int len = Math.min(elements.length, limit);
for (int i = 0; i < len; i++) {
log.error(elements[i].toString());
}
```

#1: Initial revision by

hkotsubo‭ · 2024-02-28T16:52:54Z (2 months ago)

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It's not clear where this stack trace comes from (either from an exception or the current thread), but it doesn't matter, the way to do it is the same.

Both `Exception`'s and `Thread`'s have the `getStackTrace()` method. For the current thread, you can use `Thread.currentThread().getStackTrace()`, but you can call the method for any other thread as well.

In either case, the `getStackTrace` method will return an array of `StackTraceElement`'s. Just remind that, for threads, it'll return an a zero-length array if the thread has not started, has started but has not yet been scheduled to run by the system, or has terminated.

Anyway, once you have the array, it's very straighforward to log the first N lines:

```java
int limit = 5; // number of elements to log

// Get the stack trace from an exception
// or use Thread.currentThread().getStackTrace() to get from the current thread
// or simply thread.getStackTrace() to get from any other thread
StackTraceElement[] elements = exception.getStackTrace();

// just in case the array has fewer elements than the limit
int len = Math.min(elements.length, limit);
for (int i = 0; i < len; i++) {
    log.error(elements[i].toString());
}
```

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