How to Handle Frequent Full GC and High CPU Usage in Java Backend Development

Problem 1: How to deal with frequent Full GC in production?

Full GC is the most painful type of garbage collection in Java because it pauses the application to clean the entire heap.

1.1 Identify the causes of frequent Full GC

Common reasons include:

Heap size too small.

Too many objects not reclaimed promptly.

Memory leaks caused by lingering strong references.

1.2 Adjust JVM parameters

Typical JVM options to mitigate Full GC:

-Xms512m   # initial heap size
-Xmx2g     # maximum heap size
-Xmn512m   # young generation size
-XX:+UseG1GC  # enable G1 garbage collector

G1GC is recommended because it reduces pause times for large applications.

1.3 Avoid memory leaks

Common leak scenarios include static collections holding many objects and unremoved event listeners.

Use tools such as JVisualVM or MAT to analyze the heap and ensure no unnecessary strong references remain.

// Check whether an object is properly cleared
List
objects = new ArrayList<>();
objects.add(new Object());
objects.clear(); // ensure the list is cleared after use

Problem 2: How to handle high CPU usage?

2.1 Identify the reasons for high CPU

Infinite loops that keep the CPU busy.

Thread contention and excessive context switching.

High‑frequency calculations or blocking I/O operations.

while (true) {
    // endless loop keeps CPU at high load
}

2.2 Use performance analysis tools

JVM profiling tools such as JVisualVM and JProfiler can show real‑time memory, thread, and CPU usage.

2.3 Optimize high‑CPU code

Improve algorithms and cache results to avoid repeated work.

Use asynchronous execution with thread pools, CompletableFuture, or ExecutorService.

Reduce lock contention by using finer‑grained locks or lock‑free algorithms.

2.4 Adjust JVM parameters for CPU

Setting an appropriate thread stack size can reduce resource waste:

-XX:ThreadStackSize=256k  # set thread stack size

Conclusion

In Java backend development, frequent Full GC usually stems from inadequate heap settings or memory leaks, while high CPU usage often results from inefficient algorithms or resource contention. Proper JVM tuning, code optimization, and the use of profiling tools are essential for maintaining stable and efficient systems.