java创建文件占用内存吗

java创建文件必须要对内存进行空间的分配和管理，不过占用内存不多，通常是40个字节。

Java是一门面向对象编程语言，1990年代初由詹姆斯高斯林等人开发出Java语言的雏形，最初被命名为Oak，后随着互联网的发展，经过对Oak的改造，1995年5月Java正式发布。

首先

创建一个Bean用来存贮要得到的信

public class MonitorInfoBean {

/** 可使用内存. */

private long totalMemory

/** 剩余内存. */

private long freeMemory

/** 最大可使用内存. */

private long maxMemory

/** *** 作系统. */

private String osName

/** 总的物理内存. */

private long totalMemorySize

/** 剩余的物理内存. */

private long freePhysicalMemorySize

/** 已使用的物理内存. */

private long usedMemory

/** 线程总数. */

private int totalThread

/** cpu使用率. */

private double cpuRatio

public long getFreeMemory() {

return freeMemory

}

public void setFreeMemory(long freeMemory) {

this.freeMemory = freeMemory

}

public long getFreePhysicalMemorySize() {

return freePhysicalMemorySize

}

public void setFreePhysicalMemorySize(long freePhysicalMemorySize) {

this.freePhysicalMemorySize = freePhysicalMemorySize

}

public long getMaxMemory() {

return maxMemory

}

public void setMaxMemory(long maxMemory) {

this.maxMemory = maxMemory

}

public String getOsName() {

return osName

}

public void setOsName(String osName) {

this.osName = osName

}

public long getTotalMemory() {

return totalMemory

}

public void setTotalMemory(long totalMemory) {

this.totalMemory = totalMemory

}

public long getTotalMemorySize() {

return totalMemorySize

}

public void setTotalMemorySize(long totalMemorySize) {

this.totalMemorySize = totalMemorySize

}

public int getTotalThread() {

return totalThread

}

public void setTotalThread(int totalThread) {

this.totalThread = totalThread

}

public long getUsedMemory() {

return usedMemory

}

public void setUsedMemory(long usedMemory) {

this.usedMemory = usedMemory

}

public double getCpuRatio() {

return cpuRatio

}

public void setCpuRatio(double cpuRatio) {

this.cpuRatio = cpuRatio

}

}

之后，建立bean的接口

public interface IMonitorService {

public MonitorInfoBean getMonitorInfoBean() throws Exception

}

然后，就是最关键的，得到cpu的利用率，已用内存，可用内存，最大内存等信息。

import java.io.InputStreamReader

import java.io.LineNumberReader

import sun.management.ManagementFactory

import com.sun.management.OperatingSystemMXBean

import java.io.*

import java.util.StringTokenizer

/**

* 获取系统信息的业务逻辑实现类.

* @author GuoHuang

*/

public class MonitorServiceImpl implements IMonitorService {

private static final int CPUTIME = 30

private static final int PERCENT = 100

private static final int FAULTLENGTH = 10

private static final File versionFile = new File("/proc/version")

private static String linuxVersion = null

/**

* 获得当前的监控对象.

* @return 返回构造好的监控对象

* @throws Exception

* @author GuoHuang

*/

public MonitorInfoBean getMonitorInfoBean() throws Exception {

int kb = 1024

// 可使用内存

long totalMemory = Runtime.getRuntime().totalMemory() / kb

// 剩余内存

long freeMemory = Runtime.getRuntime().freeMemory() / kb

// 最大可使用内存

long maxMemory = Runtime.getRuntime().maxMemory() / kb

OperatingSystemMXBean osmxb = (OperatingSystemMXBean) ManagementFactory

.getOperatingSystemMXBean()

// *** 作系统

String osName = System.getProperty("os.name")

// 总的物理内存

long totalMemorySize = osmxb.getTotalPhysicalMemorySize() / kb

// 剩余的物理内存

long freePhysicalMemorySize = osmxb.getFreePhysicalMemorySize() / kb

// 已使用的物理内存

long usedMemory = (osmxb.getTotalPhysicalMemorySize() - osmxb

.getFreePhysicalMemorySize())

/ kb

// 获得线程总数

ThreadGroup parentThread

for (parentThread = Thread.currentThread().getThreadGroup()parentThread

.getParent() != nullparentThread = parentThread.getParent())

int totalThread = parentThread.activeCount()

double cpuRatio = 0

if (osName.toLowerCase().startsWith("windows")) {

cpuRatio = this.getCpuRatioForWindows()

}

else {

cpuRatio = this.getCpuRateForLinux()

}

// 构造返回对象

MonitorInfoBean infoBean = new MonitorInfoBean()

infoBean.setFreeMemory(freeMemory)

infoBean.setFreePhysicalMemorySize(freePhysicalMemorySize)

infoBean.setMaxMemory(maxMemory)

infoBean.setOsName(osName)

infoBean.setTotalMemory(totalMemory)

infoBean.setTotalMemorySize(totalMemorySize)

infoBean.setTotalThread(totalThread)

infoBean.setUsedMemory(usedMemory)

infoBean.setCpuRatio(cpuRatio)

return infoBean

}

private static double getCpuRateForLinux(){

InputStream is = null

InputStreamReader isr = null

BufferedReader brStat = null

StringTokenizer tokenStat = null

try{

System.out.println("Get usage rate of CUP , linux version: "+linuxVersion)

Process process = Runtime.getRuntime().exec("top -b -n 1")

is = process.getInputStream()

isr = new InputStreamReader(is)

brStat = new BufferedReader(isr)

if(linuxVersion.equals("2.4")){

brStat.readLine()

brStat.readLine()

brStat.readLine()

brStat.readLine()

tokenStat = new StringTokenizer(brStat.readLine())

tokenStat.nextToken()

tokenStat.nextToken()

String user = tokenStat.nextToken()

tokenStat.nextToken()

String system = tokenStat.nextToken()

tokenStat.nextToken()

String nice = tokenStat.nextToken()

System.out.println(user+" , "+system+" , "+nice)

user = user.substring(0,user.indexOf("%"))

system = system.substring(0,system.indexOf("%"))

nice = nice.substring(0,nice.indexOf("%"))

float userUsage = new Float(user).floatValue()

float systemUsage = new Float(system).floatValue()

float niceUsage = new Float(nice).floatValue()

return (userUsage+systemUsage+niceUsage)/100

}else{

brStat.readLine()

brStat.readLine()

tokenStat = new StringTokenizer(brStat.readLine())

tokenStat.nextToken()

tokenStat.nextToken()

tokenStat.nextToken()

tokenStat.nextToken()

tokenStat.nextToken()

tokenStat.nextToken()

tokenStat.nextToken()

String cpuUsage = tokenStat.nextToken()

System.out.println("CPU idle : "+cpuUsage)

Float usage = new Float(cpuUsage.substring(0,cpuUsage.indexOf("%")))

return (1-usage.floatValue()/100)

}

} catch(IOException ioe){

System.out.println(ioe.getMessage())

freeResource(is, isr, brStat)

return 1

} finally{

freeResource(is, isr, brStat)

}

}