Table of contents

Java

java command

run the class boot.Main with the current directory as classpath

java boot.Main -cp .

run a standalone jar

java -jar myjar.jar

show garbage collection

-verbose:gc

Thread dumps

have linux process with id [pid] dump its threads to the console

kill -3 [pid]
jstack [id]

lazy method, simply force all java processes to make thread dumps (not for production)

pkill -3 java

thread dump analysis

http://fastthread.io/

Manifest

specifying a main class

Main-Class: com.example.Type

Unused imports

a simple script for removing unused imports

https://gist.github.com/rodrigosetti/4734557

dealing with warnings

ignoring heap pollution warning

@SafeVarargs

ignoring compiler warnings

@SuppressWarnings("[value]")

valid values

https://stackoverflow.com/questions/1205995/what-is-the-list-of-valid-suppresswarnings-warning-names-in-java

Print JavaBean properties

public static void dump(Object obj) {
	Map<String, Object> map = new HashMap<>();

        for (Method method : obj.getClass().getMethods()) {
            try {
                if (method.getName().startsWith("get") && method.getParameters().length == 0) {
                    method.setAccessible(true);
                    Object result = method.invoke(obj, new Object[] {});
                    map.put(method.getName(), result);
                }
            } catch (Exception e) {
                System.out.println("## " + method.getName() + " ##");
                e.printStackTrace();
                System.out.println();
            }
        }
        map.forEach((key, value) -> System.out.println(key + " => " + value));
}