Calendar

Calendar c = Calendar.getInstance();//        Calendar c = new GregorianCalendar();                int year = c.get(Calendar.YEAR);//年        int month = c.get(Calendar.MONTH);//月        int day = c.get(Calendar.DAY_OF_MONTH);//日        int hour = c.get(Calendar.HOUR_OF_DAY);//時        int minute = c.get(Calendar.MINUTE);//分        int second = c.get(Calendar.SECOND);//秒        int millisecond = c.get(Calendar.MILLISECOND);//毫秒        //星期        String[] weeks = {"星期日","星期一","星期二","星期三","星期四","星期五","星期六"};        int week = c.get(Calendar.DAY_OF_WEEK);                StringBuilder sb = new StringBuilder();      sb.append(year).append("年").append(month).append("月").append(day).append("日  ")        .append(hour).append(":").append(minute).append(":").append(second).append(" ")        .append(millisecond).append(" ").append(weeks[week]);                System.out.println(sb.toString());

DateFormat

//        DateFormat df = DateFormat.getDateInstance();        //參數（指定日期風格，指定語言環境）//        DateFormat df = DateFormat.getDateInstance(DateFormat.LONG, Locale.CHINA);//        DateFormat df = DateFormat.getTimeInstance();        DateFormat df = DateFormat.getTimeInstance(DateFormat.LONG, Locale.getDefault());                String nowDate = df.format(new Date());        System.out.println("當前日期為："+nowDate);

SimpleDateFormat

//用默認的模式和默認語言環境的日期格式符號構造 SimpleDateFormat。//        SimpleDateFormat sdf = new SimpleDateFormat();        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss SSS");                String s = sdf.format(new Date());        System.out.println(s);

Comparator

/** * 人類 * 如果自定義類的對象要實現排序（比較）,那么就要實現Comparable接口，并實現接口的 * compareTo方法 */public class Person implements Comparable<Person>{    private String name;    private int age;        public Person() {    }    public Person(String name, int age) {        this.name = name;        this.age = age;    }        public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    @Override    public String toString() {        return "Person [name=" + name + ", age=" + age + "]";    }    //比較器的比較方法    //如果當前對象小于參數對象，返回-1    //如果當前對象等于參數對象，返回0    //如果當前對象大于參數對象，返回1    @Override    public int compareTo(Person o) {        //實現：定義對象之間的比較規則        if(o==null){            throw new NullPointerException();        }        if(this.age<o.age){            return -1;        }else if(this.age>o.age){            return 1;        }                return 0;    }}

/** * 人類*/public class Person2{    private String name;    private int age;            public Person2() {    }    public Person2(String name, int age) {        this.name = name;        this.age = age;    }        public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    @Override    public String toString() {        return "Person [name=" + name + ", age=" + age + "]";    }}

/** * 自定義的類比較器 */public class Person2Comparator implements Comparator<Person2>{    @Override    public int compare(Person2 o1, Person2 o2) {        if(o1==null || o2==null){            throw new NullPointerException();        }        if(o1.getAge()<o2.getAge()){            return -1;        }else if(o1.getAge()>o2.getAge()){            return 1;        }        return 0;    }}

//對象的排序public class PersonSortDemo {    public static void main(String[] args) {        String[] names = {"張三","李四","王五","劉備","張飛","關羽"};                Person[] persons = {                 new Person("張三", 27), new Person("李四", 29),                new Person("王五", 41), new Person("劉備", 33),                new Person("張飛", 25), new Person("關羽", 30) };                Person2[] persons2 = {                 new Person2("張三", 27), new Person2("李四", 29),                new Person2("王五", 41), new Person2("劉備", 33),                new Person2("張飛", 25), new Person2("關羽", 30) };                    Arrays.sort(names);        System.out.println(Arrays.toString(names));                //自定義類對象數組排序        Arrays.sort(persons);        System.out.println(Arrays.toString(persons));                //使用自定義的比較器        Arrays.sort(persons2, new Person2Comparator());        System.out.println(Arrays.toString(persons2));                    }}

Clone

/** * 一個類要想實現克隆功能，必須： * 1、實現Cloneable接口，該接口是一個標記接口 * 2、重寫Object類中的clone方法 */public class Cat implements Cloneable{    private String name;    private int age;        public Cat(String name, int age) {        super();        this.name = name;        this.age = age;    }        public Cat() {        super();    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    @Override    public String toString() {        return "Cat [name=" + name + ", age=" + age + "]";    }    //重寫Object的clone方法    @Override    protected Object clone() throws CloneNotSupportedException {        return super.clone();    }    }

//要創建一組類似的對象，那么從性能上考慮，就可以使用克隆技術public class Test {    public static void main(String[] args) {        Cat c = new Cat("張三",3);        System.out.println("c="+c);        try {            Cat c1 = (Cat)c.clone();            System.out.println("c1="+c1);        } catch (CloneNotSupportedException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}

我是天王蓋地虎的分割線