Class:NetUtils.java
import java.io.DataInputStream; import java.io.DataOutputStream; import java.net.HttpURLConnection; import java.net.URL; import java.util.Map; import java.util.Properties; public class NetUtils { public static final String CHARACTER_ENCODING = "UTF-8"; public static final String PATH_SIGN = "/"; public static final String METHOD_POST = "POST"; public static final String METHOD_GET = "GET"; public static final String CONTENT_TYPE = "Content-Type"; /** * 以POST方式向指定地址发送数据包请求,并取得返回的数据包 * * @param urlString * @param requestData * @return 返回数据包 * @throws Exception */ public static byte[] requestPost(String urlString, byte[] requestData) throws Exception { Properties requestProperties = new Properties(); requestProperties.setProperty(CONTENT_TYPE, "application/octet-stream; charset=utf-8"); return requestPost(urlString, requestData, requestProperties); } /** * 以POST方式向指定地址发送数据包请求,并取得返回的数据包 * * @param urlString * @param requestData * @param requestProperties * @return 返回数据包 * @throws Exception */ public static byte[] requestPost(String urlString, byte[] requestData, Properties requestProperties) throws Exception { byte[] responseData = null; HttpURLConnection con = null; try { URL url = new URL(urlString); con = (HttpURLConnection) url.openConnection(); //设置请求属性 if ((requestProperties != null) && (requestProperties.size() > 0)) { for (Map.Entry<Object, Object> entry : requestProperties.entrySet()) { String key = String.valueOf(entry.getKey()); String value = String.valueOf(entry.getValue()); con.setRequestProperty(key, value); } } con.setRequestMethod(METHOD_POST); // 置为POST方法 con.setDoInput(true); // 开启输入流 con.setDoOutput(true); // 开启输出流 // 如果请求数据不为空,输出该数据。 if (requestData != null) { DataOutputStream dos = new DataOutputStream(con.getOutputStream()); dos.write(requestData); dos.flush(); dos.close(); } int length = con.getContentLength(); // 如果回复消息长度不为-1,读取该消息。 if (length != -1) { DataInputStream dis = new DataInputStream(con.getInputStream()); responseData = new byte[length]; dis.readFully(responseData); dis.close(); } } catch (Exception e) { throw e; } finally { if (con != null) { con.disconnect(); con = null; } } return responseData; } }

JVMmanagesgarbagecollectionacrossplatformseffectivelybyusingagenerationalapproachandadaptingtoOSandhardwaredifferences.ItemploysvariouscollectorslikeSerial,Parallel,CMS,andG1,eachsuitedfordifferentscenarios.Performancecanbetunedwithflagslike-XX:NewRa

Java code can run on different operating systems without modification, because Java's "write once, run everywhere" philosophy is implemented by Java virtual machine (JVM). As the intermediary between the compiled Java bytecode and the operating system, the JVM translates the bytecode into specific machine instructions to ensure that the program can run independently on any platform with JVM installed.

The compilation and execution of Java programs achieve platform independence through bytecode and JVM. 1) Write Java source code and compile it into bytecode. 2) Use JVM to execute bytecode on any platform to ensure the code runs across platforms.

Java performance is closely related to hardware architecture, and understanding this relationship can significantly improve programming capabilities. 1) The JVM converts Java bytecode into machine instructions through JIT compilation, which is affected by the CPU architecture. 2) Memory management and garbage collection are affected by RAM and memory bus speed. 3) Cache and branch prediction optimize Java code execution. 4) Multi-threading and parallel processing improve performance on multi-core systems.

Using native libraries will destroy Java's platform independence, because these libraries need to be compiled separately for each operating system. 1) The native library interacts with Java through JNI, providing functions that cannot be directly implemented by Java. 2) Using native libraries increases project complexity and requires managing library files for different platforms. 3) Although native libraries can improve performance, they should be used with caution and conducted cross-platform testing.

JVM handles operating system API differences through JavaNativeInterface (JNI) and Java standard library: 1. JNI allows Java code to call local code and directly interact with the operating system API. 2. The Java standard library provides a unified API, which is internally mapped to different operating system APIs to ensure that the code runs across platforms.

modularitydoesnotdirectlyaffectJava'splatformindependence.Java'splatformindependenceismaintainedbytheJVM,butmodularityinfluencesapplicationstructureandmanagement,indirectlyimpactingplatformindependence.1)Deploymentanddistributionbecomemoreefficientwi

BytecodeinJavaistheintermediaterepresentationthatenablesplatformindependence.1)Javacodeiscompiledintobytecodestoredin.classfiles.2)TheJVMinterpretsorcompilesthisbytecodeintomachinecodeatruntime,allowingthesamebytecodetorunonanydevicewithaJVM,thusfulf


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