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# Operating System Information
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Operating system details, process management, file system access, and network configuration with comprehensive process monitoring capabilities.
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## OperatingSystem Interface
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Interface providing access to operating system information, processes, file systems, and network configuration.
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```java { .api }
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interface OperatingSystem {
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    String getFamily();
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    String getManufacturer();
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    OSVersionInfo getVersionInfo();
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    FileSystem getFileSystem();
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    InternetProtocolStats getInternetProtocolStats();
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    List<OSProcess> getProcesses();
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    List<OSProcess> getProcesses(Predicate<OSProcess> filter, Comparator<OSProcess> sort, int limit);
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    List<OSProcess> getProcesses(Collection<Integer> pids);
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    OSProcess getProcess(int pid);
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    List<OSProcess> getChildProcesses(int parentPid, Predicate<OSProcess> filter, Comparator<OSProcess> sort, int limit);
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    List<OSProcess> getDescendantProcesses(int parentPid, Predicate<OSProcess> filter, Comparator<OSProcess> sort, int limit);
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    int getProcessId();
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    OSProcess getCurrentProcess();
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    int getProcessCount();
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    int getThreadId();
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    OSThread getCurrentThread();
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    int getThreadCount();
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    int getBitness();
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    long getSystemUptime();
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    long getSystemBootTime();
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    boolean isElevated();
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    NetworkParams getNetworkParams();
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    List<OSService> getServices();
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    List<OSSession> getSessions();
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    List<OSDesktopWindow> getDesktopWindows(boolean visibleOnly);
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    List<ApplicationInfo> getInstalledApplications();
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}
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```
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## OS Version Information
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Operating system version details.
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```java { .api }
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class OSVersionInfo {
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    String getVersion();
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    String getCodeName();
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    String getBuildNumber();
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    String toString();
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}
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```
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## Process Information
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Information about running processes including CPU usage, memory consumption, and process relationships.
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```java { .api }
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interface OSProcess {
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    String getName();
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    String getPath();
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    String getCommandLine();
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    String getCurrentWorkingDirectory();
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    String getUser();
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    String getUserID();
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    String getGroup();
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    String getGroupID();
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    State getState();
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    int getProcessID();
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    int getParentProcessID();
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    int getThreadCount();
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    int getPriority();
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    long getVirtualSize();
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    long getResidentSetSize();
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    long getKernelTime();
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    long getUserTime();
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    long getUpTime();
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    long getStartTime();
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    long getBytesRead();
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    long getBytesWritten();
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    long getOpenFiles();
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    int getBitness();
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    long getAffinityMask();
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    double getProcessCpuLoadCumulative();
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    double getProcessCpuLoadBetweenTicks(OSProcess priorSnapshot);
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    String[] getArguments();
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    Map<String, String> getEnvironmentVariables();
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    List<OSThread> getThreadDetails();
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    int getMinorFaults();
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    int getMajorFaults();
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    long getContextSwitches();
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    enum State {
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        NEW, RUNNING, SLEEPING, WAITING, ZOMBIE, STOPPED, OTHER, INVALID
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    }
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}
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```
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## Process Filtering and Sorting
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Utility classes for filtering and sorting process lists.
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```java { .api }
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class ProcessFiltering {
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    static final Predicate<OSProcess> ALL_PROCESSES;
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    static final Predicate<OSProcess> VALID_PROCESS;
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    static final Predicate<OSProcess> NO_PARENT;
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    static final Predicate<OSProcess> BITNESS_64;
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    static final Predicate<OSProcess> BITNESS_32;
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}
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class ProcessSorting {
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    static final Comparator<OSProcess> NO_SORTING;
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    static final Comparator<OSProcess> CPU_DESC;
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    static final Comparator<OSProcess> RSS_DESC;
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    static final Comparator<OSProcess> UPTIME_ASC;
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    static final Comparator<OSProcess> UPTIME_DESC;
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    static final Comparator<OSProcess> PID_ASC;
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    static final Comparator<OSProcess> PARENTPID_ASC;
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    static final Comparator<OSProcess> NAME_ASC;
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}
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```
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## Thread Information
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Information about threads within processes.
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```java { .api }
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interface OSThread {
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    String getName();
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    int getThreadId();
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    OSProcess.State getState();
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    long getStartTime();
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    long getStartMemoryAddress();
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    long getContextSwitches();
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    long getKernelTime();
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    long getUserTime();
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    long getUpTime();
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    int getPriority();
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}
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```
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## Network Parameters
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Network configuration information.
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```java { .api }
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interface NetworkParams {
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    String getHostName();
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    String getDomainName();
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    String[] getDnsServers();
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    String getIpv4DefaultGateway();
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    String getIpv6DefaultGateway();
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}
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```
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## Internet Protocol Statistics
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Network protocol statistics and connection information.
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```java { .api }
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interface InternetProtocolStats {
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    TcpStats getTCPv4Stats();
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    TcpStats getTCPv6Stats();
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    UdpStats getUDPv4Stats();
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    UdpStats getUDPv6Stats();
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    List<IPConnection> getConnections();
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    class TcpStats {
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        long getConnectionsEstablished();
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        long getConnectionsActive();
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        long getConnectionsPassive();
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        long getConnectionFailures();
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        long getConnectionsReset();
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        long getSegmentsSent();
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        long getSegmentsReceived();
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        long getSegmentsRetransmitted();
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        long getInErrors();
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        long getOutRsts();
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    }
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    class UdpStats {
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        long getDatagramsSent();
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        long getDatagramsReceived();
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        long getDatagramsNoPort();
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        long getDatagramsReceivedErrors();
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    }
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    class IPConnection {
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        String getType();
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        String getLocalAddress();
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        int getLocalPort();
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        String getForeignAddress();
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        int getForeignPort();
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        TcpState getState();
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        int getOwningProcessId();
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        enum TcpState {
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            CLOSED, LISTEN, SYN_SENT, SYN_RECV, ESTABLISHED, FIN_WAIT_1,
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            FIN_WAIT_2, CLOSE_WAIT, CLOSING, LAST_ACK, TIME_WAIT, DELETE_TCB,
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            NONE, UNKNOWN
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        }
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    }
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}
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```
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## Services
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Operating system service information.
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```java { .api }
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interface OSService {
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    String getName();
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    int getProcessID();
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    State getState();
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    enum State {
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        RUNNING, STOPPED, START_PENDING, STOP_PENDING, CONTINUE_PENDING, PAUSE_PENDING, PAUSED
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    }
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}
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```
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## User Sessions
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Information about logged-in users.
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```java { .api }
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interface OSSession {
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    String getUserName();
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    String getTerminalDevice();
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    long getLoginTime();
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    String getHost();
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}
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```
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## Desktop Windows
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Desktop window information for GUI applications.
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```java { .api }
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interface OSDesktopWindow {
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    long getWindowId();
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    String getTitle();
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    String getCommand();
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    Rectangle getLocAndSize();
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    int getOwningProcessId();
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    long getOrder();
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    boolean isVisible();
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}
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```
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## Installed Applications
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Information about installed applications on the system.
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```java { .api }
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interface ApplicationInfo {
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    String getName();
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    String getVersion();
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    String getInstallDate();
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}
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```
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## Usage Examples
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### Basic OS Information
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```java
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import oshi.SystemInfo;
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import oshi.software.os.OperatingSystem;
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SystemInfo si = new SystemInfo();
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OperatingSystem os = si.getOperatingSystem();
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System.out.println("OS Family: " + os.getFamily());
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System.out.println("Manufacturer: " + os.getManufacturer());
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System.out.println("Version: " + os.getVersionInfo());
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System.out.println("Bitness: " + os.getBitness() + "-bit");
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System.out.println("Process Count: " + os.getProcessCount());
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System.out.println("Thread Count: " + os.getThreadCount());
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System.out.println("Uptime: " + os.getSystemUptime() + " seconds");
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```
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### Process Management
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```java
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import oshi.SystemInfo;
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import oshi.software.os.OperatingSystem;
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import oshi.software.os.OSProcess;
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SystemInfo si = new SystemInfo();
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OperatingSystem os = si.getOperatingSystem();
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// Get all processes
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List<OSProcess> processes = os.getProcesses();
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// Get top 10 processes by CPU usage
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List<OSProcess> topCpuProcesses = os.getProcesses(
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    OperatingSystem.ProcessFiltering.VALID_PROCESS,
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    OperatingSystem.ProcessSorting.CPU_DESC,
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    10
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);
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for (OSProcess process : topCpuProcesses) {
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    System.out.printf("PID: %d, Name: %s, CPU: %.1f%%, Memory: %d MB%n",
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        process.getProcessID(),
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        process.getName(),
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        process.getProcessCpuLoadCumulative() * 100,
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        process.getResidentSetSize() / 1024 / 1024
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    );
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}
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```
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### Process Filtering and Sorting
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```java
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import oshi.SystemInfo;
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import oshi.software.os.OperatingSystem;
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import oshi.software.os.OSProcess;
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SystemInfo si = new SystemInfo();
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OperatingSystem os = si.getOperatingSystem();
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// Get 64-bit processes only, sorted by memory usage
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List<OSProcess> processes64bit = os.getProcesses(
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    OperatingSystem.ProcessFiltering.BITNESS_64,
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    OperatingSystem.ProcessSorting.RSS_DESC,
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    20
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);
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// Get child processes of a specific PID
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List<OSProcess> children = os.getChildProcesses(
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    1234, // parent PID
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    OperatingSystem.ProcessFiltering.VALID_PROCESS,
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    OperatingSystem.ProcessSorting.NAME_ASC,
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    0 // no limit
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);
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```
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### Network Configuration
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```java
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import oshi.SystemInfo;
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import oshi.software.os.NetworkParams;
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SystemInfo si = new SystemInfo();
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NetworkParams netParams = si.getOperatingSystem().getNetworkParams();
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System.out.println("Hostname: " + netParams.getHostName());
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System.out.println("Domain: " + netParams.getDomainName());
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System.out.println("IPv4 Gateway: " + netParams.getIpv4DefaultGateway());
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System.out.println("IPv6 Gateway: " + netParams.getIpv6DefaultGateway());
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String[] dnsServers = netParams.getDnsServers();
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System.out.println("DNS Servers: " + Arrays.toString(dnsServers));
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```
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### User Sessions
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```java
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import oshi.SystemInfo;
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import oshi.software.os.OSSession;
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SystemInfo si = new SystemInfo();
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List<OSSession> sessions = si.getOperatingSystem().getSessions();
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for (OSSession session : sessions) {
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    System.out.printf("User: %s, Terminal: %s, Host: %s, Login Time: %s%n",
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        session.getUserName(),
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        session.getTerminalDevice(),
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        session.getHost(),
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        new Date(session.getLoginTime() * 1000)
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    );
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}
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```
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### Current Process Information
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```java
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import oshi.SystemInfo;
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import oshi.software.os.OperatingSystem;
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import oshi.software.os.OSProcess;
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SystemInfo si = new SystemInfo();
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OperatingSystem os = si.getOperatingSystem();
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// Get current process info
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int currentPid = os.getProcessId();
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OSProcess currentProcess = os.getCurrentProcess();
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System.out.println("Current PID: " + currentPid);
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System.out.println("Process Name: " + currentProcess.getName());
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System.out.println("Command Line: " + currentProcess.getCommandLine());
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System.out.println("Working Directory: " + currentProcess.getCurrentWorkingDirectory());
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System.out.println("User: " + currentProcess.getUser());
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```