我想得到一个物体的大小.我试着用这个方法:
import java.lang.instrument.Instrumentation; public class ObjectSizeFetcher { private static Instrumentation instrumentation; public static void premain(String args, Instrumentation inst) { instrumentation = inst; } public static long getObjectSize(Object o) { return instrumentation.getObjectSize(o); } }
但它抛出了这个错误:
java.lang.NullPointerException test.ObjectSizeFetcher.getObjectSize(ObjectSizeFetcher.java:13) servlet.testObj.doGet(cms.java:55) javax.servlet.http.HttpServlet.service(HttpServlet.java:621) javax.servlet.http.HttpServlet.service(HttpServlet.java:728) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:176) org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:145) org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:92) org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:394)
但是我尝试了jprofiler和MAT,但是我无法找到这个对象...
我能做什么?