How to use Thread Dump in java

Description

1. ThreadDump is used to diagnose problems in Java applications. It can be used to find memory leaks, discover deadlock threads, etc.

2. The system can obtain threads, thread running status, identification, calls and other information, including the complete class name, execution method, number of lines of source code, etc.

Features

can be used in various operating systems;

can be used in various Java application servers;

can be used in Use without affecting system performance;

The problem can be directly located on the code line of the application.

Example

public class JStack {
            public static void main(String[] args) throws Exception {
               ...
                    String pid = args[optionCount];
                    String params[];
                    if (locks) {
                        params = new String[] { "-l" };
                    } else {
                        params = new String[0];
                    }
                    runThreadDump(pid, params);
                ...
            }
            // Attach to pid and perform a thread dump
            private static void runThreadDump(String pid, String args[])
                    throws Exception {
                VirtualMachine vm = null;
                try {
                    vm = VirtualMachine.attach(pid);
                } catch (Exception x) {
                   ...
                }
                // Cast to HotSpotVirtualMachine as this is implementation specific
                // method.
                InputStream in = ((HotSpotVirtualMachine) vm)
                        .remoteDataDump((Object[]) args);
                // read to EOF and just print output
                byte b[] = new byte[256];
                int n;
                do {
                    n = in.read(b);
                    if (n > 0) {
                        String s = new String(b, 0, n, "UTF-8");
                        System.out.print(s);
                    }
                } while (n > 0);
                in.close();
                vm.detach();
            }

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