Mastering the JVM to Solve Problems: Common Troubleshooting Guide Common Failures: OutOfMemoryError: Out of Memory StackOverflowError: Stack Overflow NullPointerException: Access to Null Reference ClassCastException: Type Conversion Error Troubleshooting Tips: Enable Logging Analyze Heap Dumps Updated with Performance Monitoring Tools JVM Practical Example: Get a heap dump and use tools to analyze the heap to identify NullPointerException issues Fix errors by checking for null values
Take control of the JVM and solve problems: Common Troubleshooting Guide
JVM is the Java Virtual Machine, which is the platform on which Java programs run. It is responsible for loading, executing and validating Java bytecode. The JVM can encounter various failures, and understanding and resolving these failures is critical to ensuring the stability of your Java program.
Common faults
Troubleshooting Tips
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Practical Case
Consider a program that returns NullPointerException:public class Example { public static void main(String[] args) { String name = null; System.out.println(name.length()); } }A heap dump can be generated by running the following command:
jmap -dump:live,format=b,file=heap.bin <PID>Use tools such as JVisualVM to open the heap dump, and you can see that the
name variable is indeed null.
Fix
To fix this bug, you need to check thename variable and make sure it is not null before using:
public class Example { public static void main(String[] args) { String name = null; if (name != null) { System.out.println(name.length()); } } }
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