Methods

// (1) make sure the code only runs on mac os x
boolean mrjVersionExists = System.getProperty("mrj.version") != null;
boolean osNameExists = System.getProperty("os.name").startsWith("Mac OS");
if ( !mrjVersionExists || !osNameExists) {
    System.err.println("Not running on a Mac OS X system.");
    System.exit(1);
}

// (2) do all the logfile setup stuff
int currentLoggingLevel = DEFAULT_LOG_LEVEL;
File errorFile = new File(ERROR_LOG_FILENAME);
File warningFile = new File(WARNING_LOG_FILENAME);
File debugFile = new File(DEBUG_LOG_FILENAME);
// order of checks is important; want to go with more granular if multiple files exist
if (errorFile.exists()) currentLoggingLevel = DDLoggerInterface.LOG_ERROR;
if (warningFile.exists()) currentLoggingLevel = DDLoggerInterface.LOG_WARNING;
if (debugFile.exists()) currentLoggingLevel = DDLoggerInterface.LOG_DEBUG;
logger = new DDSimpleLogger(CANON_DEBUG_FILENAME, currentLoggingLevel, true, true);

// (3, 4) do all the preferences stuff, and get the default color
preferences = Preferences.userNodeForPackage(this.getClass());
int r = preferences.getInt(CURTAIN_R, 0);
int g = preferences.getInt(CURTAIN_G, 0);
int b = preferences.getInt(CURTAIN_B, 0);
int a = preferences.getInt(CURTAIN_A, 255);
currentColor = new Color(r,g,b,a);

dieIfNotRunningOnMacOsX();
connectToLogfile();
connectToPreferences();
getDefaultColor();

тип_возвращаемого_значения название_метода([параметры]) {
    // тело метода
}

public static void main(String[] args) {
    System.out.println("Hell to World!");
}

public class Program {
    public static void main(String[] args) {
        //TODO
    }

    static void hello() {
        System.out.println("Hello");
    }

    static void welcome() {
        System.out.println("Welcome to Java 11");
    }
}

имя_метода(аргументы);

public class Program {
    public static void main(String[] args) {
        hello();
        welcome();
        welcome();
    }

    static void hello() {
        System.out.println("Hello");
    }

    static void welcome() {
        System.out.println("Welcome to Java 11");
    }
}

Hello
Welcome to Java 11
Welcome to Java 11

static void sum(int x, int y) {
    int z = x + y;
    System.out.println(z);
}

public class Program {
    public static void main(String[] args) {
        int a = 6;
        int b = 8;
        sum(a, b); // 14
        sum(3, a); // 9
        sum(5, 23); // 28
    }

    static void sum(int x, int y) {
        int z = x + y;
        System.out.println(z);
    }
}

public class Program {
    public static void main(String[] args) {
        display("Tom", 34);
        display("Bob", 28);
        display("Sam", 23);
    }

    static void display(String name, int age) {
        System.out.println(name);
        System.out.println(age);
    }
}

public class Program {
    public static void main(String[] args) {
        int x = sum(1, 2, 3);
        int y = sum(2, 4, 9);
        System.out.println(x); // 6
        System.out.println(y); // 15
    }

    static int sum(int a, int b, int c) {
        return a + b + c;
    }
}