纸上得来终觉浅，绝知此事要躬行。

LocalDate类的使用

/**
     * 让我们手写一个日历吧
     * @param args
     */
    public static void main(String[] args) {
        LocalDate date = LocalDate.now();
        int month = date.getMonthValue();
        int today = date.getDayOfMonth();
        
        date = date.minusDays(today - 1);    // Set to start of month
        DayOfWeek weekday = date.getDayOfWeek();
        int value = weekday.getValue();        // 1 = Monday ...7 = Sunday
        
        System.out.println("Mon Tue Mon Thu Fri Sat Sun");
        for(int i = 1; i < value; i ++)
            System.out.print("    ");
        while (date.getMonthValue() == month) 
        {
            System.out.printf("%3d", date.getDayOfMonth());
            if (date.getDayOfMonth() == today) 
                System.out.print("*");
            else
                System.out.print(" ");
            date = date.plusDays(1);
            if (date.getDayOfWeek().getValue() == 1) System.out.println();
        }
        if (date.getDayOfWeek().getValue() != 1) {
            System.out.println();
        }
    }

显示效果：

EmployeeTest

public class EmployeeTest {

    public static void main(String[] args) {
        // fill the staff array with three Employee objects
        Employee[] staff = new Employee[3];
        
        staff[0] = new Employee("Carl Cracker", 75000, 1987, 12, 15);
        staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
        staff[2] = new Employee("Tony Tester", 40000, 1990, 3, 15);
        
        // raise everyone's salary by 5%
        for(Employee e : staff) {
            e.raiseSalary(5);
        }
        
        // print out information about all Employee objects
        for(Employee e : staff) {
            System.out.println("name=" + e.getName()+",salary=" + e.getSalary() + ",hireDay="+ e.getHireDay());
        }
    }
    
    
}

class Employee
{
    private String name;
    private double salary;
    private LocalDate hireDay;
    
    public Employee(String name, double salary, int year, int month, int day) {
        super();
        this.name = name;
        this.salary = salary;
        this.hireDay = LocalDate.of(year, month, day);
    }

    public String getName() {
        return name;
    }

    public double getSalary() {
        return salary;
    }

    public LocalDate getHireDay() {
        return hireDay;
    }
    
    public void raiseSalary(double byPercent) 
    {
        double raise = salary * byPercent / 100;
        salary += salary;
    }
    
}

 StaticTest

public class StaticTest {
    public static void main(String[] args) {
        // fill the staff array with three Employee objects
        Employee[] staff = new Employee[3];
        
        staff[0] = new Employee("Tom", 40000);
        staff[1] = new Employee("Dick", 60000);
        staff[2] = new Employee("Harry", 65000);
        
        // print out information about all Employee objects
        for (Employee e : staff) {
            e.setId();
            System.out.println("name = " + e.getName() + ", id = " + e.getId() +", salary = " + e.getSalary());;
        }
        
        int n = Employee.getNextId();    // call static method
        System.out.println("Next avaliable id=" + n);
    }
    
}

class Employee
{
    private static int nextId = 1;
    
    private String name;
    private double salary;
    private int id;
    
    public Employee(String name, double salary) {
        super();
        this.name = name;
        this.salary = salary;
        this.id = 0;
    }

    public String getName() {
        return name;
    }

    public double getSalary() {
        return salary;
    }

    public int getId() {
        return id;
    }
    
    public void setId()
    {
        id = nextId;    // set id to next avaliable id
        nextId++;
    }
    
    public static int getNextId() {
        return nextId;    // return static field
    }
    
    public static void main(String[] args) {
        Employee employee = new Employee("Harry", 50000);
        System.out.println(employee.getName() + " " + employee.getSalary());
    }
    
    
}

public class StaticTest {
    public static void main(String[] args) {
        // fill the staff array with three Employee objects
        Employee[] staff = new Employee[3];
        
        staff[0] = new Employee("Tom", 40000);
        staff[1] = new Employee("Dick", 60000);
        staff[2] = new Employee("Harry", 65000);
        
        // print out information about all Employee objects
        for (Employee e : staff) {
            e.setId();
            System.out.println("name = " + e.getName() + ", id = " + e.getId() +", salary = " + e.getSalary());;
        }
        
        int n = Employee.getNextId();    // call static method
        System.out.println("Next avaliable id=" + n);
    }
    
}

class Employee
{
    private static int nextId = 1;
    
    private String name;
    private double salary;
    private int id;
    
    public Employee(String name, double salary) {
        super();
        this.name = name;
        this.salary = salary;
        this.id = 0;
    }

    public String getName() {
        return name;
    }

    public double getSalary() {
        return salary;
    }

    public int getId() {
        return id;
    }
    
    public void setId()
    {
        id = nextId;    // set id to next avaliable id
        nextId++;
    }
    
    public static int getNextId() {
        return nextId;    // return static field
    }
    
    public void raiseSalary(double byPercent) 
    {
        double raise = salary * byPercent / 100;
        salary += raise;
    }
    
    public static void tripleSalary(Employee x) {
        x.raiseSalary(200);
    }
    
    public static void main(String[] args) {
        Employee harry;
        harry = new Employee("Harry", 50000);
        tripleSalary(harry);
        System.out.println(harry.getName() + " " + harry.getSalary());
    }
    
    
}

 

public class StaticTest {
    public static void main(String[] args) {
        /**
         * Test 1: Methods can't modify numeric parameters
         */
        System.out.println("Testing tripleValue:");
        double percent = 10;
        System.out.println("Before: percent=" + percent);
        tripleValue(percent);
        System.out.println("After: percent=" + percent);
        
        /**
         * Test 2: Methods can change the state of object parameters
         */
        System.out.println("
Testing tripleSalary");
        Employee harry = new Employee("Harry", 50000);
        System.out.println("Before: salary=" + harry.getSalary());
        tripleSalary(harry);
        System.out.println("After: salary=" + harry.getSalary());
        
        /**
         * Test 3: Methods can't attach new objects to object parameters
         */
        System.out.println("
Testing swap:");
        Employee a = new Employee("Alice", 70000);
        Employee b = new Employee("Bob", 70000);
        System.out.println("Before: a=" + a.getName());
        System.out.println("Before: b=" + b.getName());
        swap(a, b);
        System.out.println("After: a=" + a.getName());
        System.out.println("After: b=" + b.getName());
        
    }
    
    public static void tripleValue(double x) {
        x = 3 * x;
        System.out.println("End of method: x=" + x);
    }
    
    public static void tripleSalary(Employee x) {
        x.raiseSalary(200);
        System.out.println("End of method: salary=" + x.getSalary());
    }
    
    public static void swap(Employee x, Employee y) {
        Employee temp = x;
        x = y;
        y = temp;
        System.out.println("End of method: x=" + x.getName());
        System.out.println("End of method: y=" + y.getName());
    }
    
}

class Employee        // simplfied Employee class
{    
    private String name;
    private double salary;
    
    public Employee(String name, double salary) {
        super();
        this.name = name;
        this.salary = salary;
    }

    public String getName() {
        return name;
    }

    public double getSalary() {
        return salary;
    }

    
    public void raiseSalary(double byPercent) 
    {
        double raise = salary * byPercent / 100;
        salary += raise;
    }
}