What is Java Heap Space? And how to solve it?

We all know that Java applications use a limited amount of memory. This java memory is separated into different heap stacks. And this stack is called Heap space and Permgen .

The purpose of this memory sharing is to run the application optimally. Whenever we declare new variables and objects, be it calling , performing similar operations, declaring String, java will point memory to these operations from Stack Memory or Heap Space. This restriction is determined during the startup of the running application which aims to be more complex.

Causes of Java Heap Space

The reason this java.lang.OutOfMemoryError: Java heap space error occurs is because you are trying to load an XXL application into Java heap space of size S. Because the application simply needs more Java heap space than is available to operate normally.

Another cause for this OutOfMemoryError message is more complex and is caused by a programming error: A spike in data usage/volume.

Applications are designed to handle a certain number of users or a certain amount of data. When the number of users or data volume suddenly spikes and crosses the expected threshold, operations that were normally functioning before the spike stop operating and trigger a java.lang.OutOfMemoryError: Java heap space error.

Certain types of programming errors will constantly make your application use more memory. Whenever the functionality leaks from the application is used, it leaves some objects into the Java heap space. Over time, the leaked object consumes all available Java heap space and triggers java.lang.OutOfMemoryError: a known Java heap space error.

Java Heap Memory Function

  • If the heap space is full, Java throws a java.lang.OutOfMemoryError.
  • Access to this memory is relatively slower than heap memory. This memory, in contrast to heap, is not allocated automatically.
  • It takes a Garbage Collector to empty unused objects so that it can maintain efficient memory usage.
  • Unlike the stack, the heap is not threadsafe and needs to be maintained by properly synchronizing code.

How to Solve Java Heap Space

In some cases, the amount of heap you allocate to your JVM is not sufficient to accommodate the needs of your applications running on that JVM. In this case, you should allocate more heap.

However, in most cases, providing more Java heap space does not necessarily solve the problem. For example, if your application contains a memory leak then you add more heap, it will only delay java.lang.OutOfMemoryError: Java heap space error.

Additionally, increasing the amount of Java heap space also tends to increase the length of GC lags which affects your application’s throughput or latency.

If you want to solve the underlying problem with Java heap space instead of masking the symptoms, you need to figure out which part of your code is responsible for allocating the most memory. In other words, you need to do some analysis on your program.

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