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OutOfMemoryError Is this an advanced exception

Posted on Dec. 3, 2023, 7:30 p.m. by Antonio Robertson PhD
Category: The back-end Tag: The back-end

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Exception in thread "main" java.lang.OutOfMemoryError: GC overhead limit exc


  • The JVM parameter test was intended to test for an exception where the constant pool in the method area ran out of memory. But the above error was thrown.
  • First, the parameters are set as follows
Copy the code
  • -xx :MetaspaceSize=5M and -xx :MaxMetaspaceSize=10M indicate the memory size limit of the method area.
Public class RuntimeConstantError {public static void main(String[] args) {//List keeps references to the constant pool. ListString List = new ArrayList(); int i =0 ; while (true) { list.add(String.valueOf(i++).intern()); }}}Copy the code
  • Keep adding variables to the constant pool using the String. Intern method as described above. And always keep references to prevent GC. Eventually there will be a package memory overflow error. But it didn't.
  • Constant pools can be understood as temporary concentration camps, where we unify production and manage our variables


New error type in JDK6.

  • This exception is thrown when the GC takes a lot of time to free a small amount of space; When the release is very small, we can consider this GC failure

  • That is (Sun's official definition: throw this exception when more than 98% of the time is spent GC and less than 2% of the heap is reclaimed).

  • Usually because the heap is too small, the cause of the exception: there is not enough memory.

Ii. Solutions:

  • See if your system has code that uses a lot of memory or an infinite loop.
  • You can add startup parameters for the JVM to limit memory usage: -xx: -usegCoverheadLimit

Case analysis

  • By looking at the log, we can see that we are always thinking about adding variables to the constant area. We GC when we run out of memory, but we keep referencing. So the GC does not collect garbage. The number of GC is small, so the limited error will be reported. When we add UseGCOverheadLimit, we get an out-of-memory error classic error.Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
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