PlayJava Day009

Today Plant Science:

/ * 2019.08.19 started to learn, to make this shift. * /

1.Date tools:

= DATE DATE new new DATE ();   // this time 
the SimpleDateFormat SDF = new new the SimpleDateFormat ( "the MM-dd-YYYY" ); 
sdf.format (DATE) ----> Time to String 
sdf.parse (Source) - -> string transfer time

2.Object class: is the parent of all classes.

All information open classes: ctrl + o

public String toString ()   // Returns a string representation of the object 
    return  the this .getName ();   // rewritable

public boolean equals (Object obj) {
    String name = ((People)obj).getName() ;
    return this.name == name ;  //重写

3.instanceof Keywords: to determine whether an object belongs to a class.

Format: The object instanceof class ----> Boolean return type

IF (Animal the instanceof Dog) { 
    ((Dog) Animal) .func1 (); 
} 

IF (Animal the instanceof Cat) { 
    ((Cat) Animal) .func2 (); 
} 

// was used for determination downcast

4. anonymous inner classes: new interface or an abstract class.

t.test (
    new A () {
        public void a() {
        }
    }
        ) ;

The packaging added:

String a = "1" ;
String b = "2" ;
int m = Integer.parseInt(a) ;
int n = Integer.parseInt(b) ;
System.out.println(m+n) ;
----> 3

6. singleton design pattern

In Java applications, singletons can guarantee a JVM, only one instance of the object exists.

Mode: ① starving single embodiment implemented: pre-instantiated

Private Singleton1 ()   // constructor private 
Private  static  Final Singleton1 Single1 = new new Singleton1 ()
 // static factory mode: 
public  static Singleton1 the getInstance () {
     return Single1; 
}

② lazy single case realization: When the first call is instantiated (plus synchronized synchronization to avoid creating multiple simultaneous access objects)

private static Singleton2 single ;
//工厂：
public static Singleton2 getInstance() {
    if (single == null) {
        single = new Singleton2() ;
    }
    return single ;
}

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