java - 多线程-为每个循环创建新线程

Question

我对多线程了解不多，但我认为它可能对我正在做的事情有用。我有一些东西可以循环遍历 xml 文件中的每个图形节点，并根据读取的信息创建一个对象。根据对象，它可以接受一个或多个查询，或者将使用存储过程。然后该对象存储在 arrayList 中。最终我的程序需要大约一分钟才能启动。有没有一种方法可以在每次循环时创建一个新线程？这是我的代码:

            File fXmlFile = f;
            DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
            DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
            Document doc = dBuilder.parse(fXmlFile);

            //Normalize the xml file(document)
            doc.getDocumentElement().normalize();

            // All of the nodelists that the XML file uses
            NodeList graphicNodeList = doc.getElementsByTagName("graphic");
            NodeList locationNodeList = doc.getElementsByTagName("location");
            NodeList gUINodeList  = doc.getElementsByTagName("GUI");
            NodeList storedProcedureNodeList  = doc.getElementsByTagName("storedProcedure");
            NodeList parameterNodeList = doc.getElementsByTagName("parameter");
            NodeList dialSpecificNodeList = doc.getElementsByTagName("dialSpecific");
            NodeList queriesNodeList=doc.getElementsByTagName("queries");
            NodeList tickerSpecificNodeList=doc.getElementsByTagName("tickerSpecific");
            doc.getElementsByTagName("category");


            // Main loop to get information from each graphical Element.
            for (int temp = 0; temp < graphicNodeList.getLength(); temp++) {
                // Sets the node to the first item in the nodeList
                Node graphicNode = graphicNodeList.item(temp);


                String chartType;

                if (graphicNode.getNodeType() == Node.ELEMENT_NODE) {
                    // Makes an element based off the node.
                    Element eElement = (Element) graphicNode;

                    //Get the Chart type so the system knows what to do with it.
                    chartType= eElement.getAttribute("type");

                    if(chartType.equals("barChartVsTime")){
                        createBarChartVsTime(graphicNode, gUINodeList,locationNodeList, storedProcedureNodeList, parameterNodeList, eElement);
                    }
                    if(chartType.equals("sqlTable")){
                        createSQLTable(graphicNode, gUINodeList, eElement);
                    }
                    if(chartType.equals("dialChart")){
                        createDialChart(graphicNode, gUINodeList, dialSpecificNodeList, eElement);
                    }
                    if(chartType.equals("hourlyDialChart")){
                        createHourlyDialChart(graphicNode, gUINodeList, dialSpecificNodeList, eElement);
                    }
                    if(chartType.equals("colorBlock")){
                        createColorBlock(graphicNode, gUINodeList, eElement);
                    }
                    if(chartType.equals("image")){
                        createImageBlock(graphicNode, gUINodeList, eElement);
                    }
                    if(chartType.equals("threePointAverageChart")){
                        createThreePointAverageChart(graphicNode, gUINodeList,locationNodeList, storedProcedureNodeList, parameterNodeList, eElement);
                    }
                    if(chartType.equals("yieldDialChart")){
                        createYieldDialChart(graphicNode, gUINodeList, locationNodeList, storedProcedureNodeList, dialSpecificNodeList, parameterNodeList, eElement);
                    }

                    if(chartType.equals("ticker")){
                        createTicker(graphicNode, gUINodeList,tickerSpecificNodeList, queriesNodeList, eElement);
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

Answer 1

I don't know that much about multi threading but I think that it may be of use to what I am doing.

This ends up with my program taking about a minute to start

你有点超前了。您应该首先分析您的代码，看看哪里会影响性能。请查看 VisualVM 来了解这一点。您可能不小心编写了 O(n^2) 算法。

Depending on the object it can take in a querie(s) or it will use a stored procedure.

我打赌它就在这里。连接池或批处理请求可能比立即投入线程更好。