通常定义和使用Application类来描述某个系统整体的属性和行为。系统中所有用户均可以访问和使用Application，而Application中的所有配置适用到整个系统中。在此过程中，所有用户访问和使用的Application应该是同一个app实例。写出java实例，并画类图

Java实例代码如下：

public class Application {
    private static Application instance;
    private String appName;
    private String appVersion;
    private boolean isDebugMode;

    private Application() {
        this.appName = "MyApp";
        this.appVersion = "1.0";
        this.isDebugMode = false;
    }

    public static synchronized Application getInstance() {
        if (instance == null) {
            instance = new Application();
        }
        return instance;
    }

    public String getAppName() {
        return appName;
    }

    public void setAppName(String appName) {
        this.appName = appName;
    }

    public String getAppVersion() {
        return appVersion;
    }

    public void setAppVersion(String appVersion) {
        this.appVersion = appVersion;
    }

    public boolean isDebugMode() {
        return isDebugMode;
    }

    public void setDebugMode(boolean debugMode) {
        isDebugMode = debugMode;
    }
}

类图如下：

---------------------
|     Application    |
---------------------
| -instance: Application |
| -appName: String |
| -appVersion: String |
| -isDebugMode: boolean |
---------------------
| +getInstance(): Application |
| +getAppName(): String |
| +setAppName(String): void |
| +getAppVersion(): String |
| +setAppVersion(String): void |
| +isDebugMode(): boolean |
| +setDebugMode(boolean): void |
---------------------