java 常用的类

一、日期操作：Calendar类和SimpleDateFormat类

    public void Test1()
    {
        Calendar calendar=Calendar.getInstance();
        System.out.println(calendar.get(Calendar.DATE));
        System.out.println(calendar.get(Calendar.DAY_OF_MONTH));
        System.out.println(calendar.get(Calendar.DAY_OF_WEEK));
        System.out.println(calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH));
        System.out.println(calendar.get(Calendar.DAY_OF_YEAR));
    }

二、Arrays类

    //数组排序
    public void Test2()
    {
        String[] strings= {"德布劳内","梅西","萨拉赫","卢卡库"};
        Arrays.sort(strings);
        System.out.println(Arrays.asList(strings));
    }
    
    //数组填充
    public void Test3()
    {
        int[] num=new int[4];
        String[] strings=new String[4];
        Arrays.fill(num, 4);
        System.out.println(Arrays.toString(num));
    }
    
    //数组比较
    public void Test4()
    {
        int[] num1=new int[5];
        int[] num2=new int[5];
        Arrays.fill(num1, 110);
        Arrays.fill(num2, 110);
        System.out.println(Arrays.equals(num1, num2));
    }

三、Java 注释

public class Annotation {

    //方法重写
    @Override
    public String toString()
    {
        return "rubbish";
    }
    
    //不建议使用
    @Deprecated
    public void TestMethod()
    {
        System.out.println("你是不是傻");
    }
    
    //屏蔽编译警告信息
    @SuppressWarnings(value="unchecked")
    public void Method2()
    {
        System.out.println("就此结束");
    }
    
    public void Test1()
    {
        String string="Color";
        string.toString();
        System.out.println(string);
    }
    
    public static void main(String[] args)
    {
        Annotation obj=new Annotation();
        obj.Method2();
    }
}

四、常用类

1）Object类

主要的方法：clone()、equals()、hashCode()、toString()

2)获取键盘输入

    //Scanner获取键盘输入
    public void Test2()
    {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) 
        {
            String str = sc.next();
            System.out.println(str);
        }
    }
    
    //BufferedReader获取键盘输入
    public void Test3() throws IOException
    {
        BufferedReader bReader=new BufferedReader(new InputStreamReader(System.in));
        
        String string=null;
        string=bReader.readLine();
        System.out.println("you are value:"+string);
    }