Java Basics-String, Date of a common class

--------------------------------------------String Class--------------------------------------------

Main content: String, StringBuffer, StringBuilder, String.Format ()

StringBuffer is thread-safe, StringBuilder is not, but StringBuilder efficient, so more commonly

StringBuilder function is the same as Stringbufer

StringBuilder vs=new StringBuilder ();

Vs.append (7). Append ("a dwarf"); 7 Little dwarves.

Vs.delete (0,2); Little Dwarf

Vs.reverse ();//Human dwarf

Vs.delete (0,vs.length ()); Empty

Vs.tostring ();//Convert to immutable string

String.Format () returns a string that functions like printf ()

Format String.Format ("[Information]< Format Control >", data list);

Format Control characters:

%d decimal

%f floating point String.Format ("%8.2f", 123456.789); 123456.78

%c character

%s string

N.M indicates that integers and decimals account for n decimal places

0 Vacant String.Format ("%012.2f", 123456.789); 000123456.78

-Align Left

n$ represents the nth data String.Format ("%1$8.2", 123456.789); 123456.78

%TF Date

%tt time String.Format ("%tt", new Date ()); 20:25:32

%ta Week

%ty year

%tm Month

--------------------------------------------the Date class-------------------------------------------

Main content: Date, DateFormat, SimpleDateFormat

Date D1=new date ();

Date D2=new date ();

Boolean flg=flase;

Long T1=d1.gettime ();//Get a Long value

Flg=d1.equals (D2);//Whether the time is the same

int X=d1.compareto (D2);//D1 is behind D2

Flg=d1.after (D2);//Ibid.

Flg=d1.before (D2);//d1 before D2

Extension: Date d3=new date (365l*24*60*60*1000); int to long put L on the front

Formatted Date (date→string)

Date D=new date ();

String str1=dateformat.getdateinstance (). Format (d); 2016-05-05

String str2=dateformat.gettimeinstance (). Format (d);//20:49:50

String str3=dateformat.getdatetimeinstance (). Format (d);//2016-05-05 20:49:50

Custom format, attention to exception handling (string→date)

Str= "2016/05/05";

D=dateformat.getdateinstace (). Parse (str1);//The format must be YYYY-MM-DD, otherwise the exception

D=new SimpleDateFormat ("Yyyy+mm+dd"). Parse (str),//STR format is not fixed, even can be "2016 Ah March Oh 2nd ah ..."

Extended:

Scanner sc=new Scanner (system.in);

String S1=sc.next (); Space

String S2=sc.nextline (); Enter

Java Basics-String, Date of a common class