SimpleDateFormat
Set the date and time you want to display the way:
import Java.text.simpledateformat;import Java.util.Date;public class Formatdemo { public static void main (string[] args) {//TODO auto-generated method stub Date d = n EW Date (); //instantiation date //yyyy represents the year, MM for the month, DD for days, minutes and seconds to say SimpleDateFormat s = new simpledateformat ( "Yyyy,MM,dd Hh:mm:SSS "); //generate the format you want to display System. out . println (S.format (d)); //date formatted }}
In addition to setting the format you want, we can also set the given string as a date:
ImportJava.text.ParseException;ImportJava.text.SimpleDateFormat;ImportJava.util.Date; Public class formatdemo { Public Static void Main(string[] args) {the date format in the//string should be the same as the date format declared below ("Yyyy,mm,dd hh:mm")String str ="2015,1,3 3:44"; SimpleDateFormat SS =NewSimpleDateFormat ("Yyyy,mm,dd hh:mm");Try{The //parse () method throws an exceptionDate dd = Ss.parse (Str.trim ()); SYSTEM.OUT.PRINTLN (DD); }Catch(ParseException e) {//TODO auto-generated catch blockE.printstacktrace (); } }}
Math
The Math class provides a number of mathematical arithmetic-related methods:
Public classMathdemo { Public Static void Main(string[] args) {//TODO auto-generated method stubSystem. out. println ("To find the absolute value of a number"+math.abs (-111)); System. out. println ("Ask for the square root of a number"+MATH.SQRT (121)); System. out. println ("To find the sine of a corner"+math.signum (Math.PI)); System. out. println ("Ask for a larger number"+math.max ( A, the));//Too many methods don't show up, check the documentation.}}
import java.util.Random;publicclass RandomDemo { publicstaticvoidmain(String[] args) { // TODO Auto-generated method stub new Random();//创建一个Random的实例 int10; //生成随机数,并打印 System.out.println("这是一个给定范围内的随机数:"+r.nextInt(x)); }}
NumberFormat
Import Java.text.NumberFormat; Public classNumberformatdemo { Public Static void Main(string[] args) {//Get the default format instanceNumberFormat n = numberformat.getinstance ();//format and outputSystem. out. println (N.format (23123123)); System. out. println (N.format (23123.123));//decimals reserved up to 3 bitsSystem. out. println (N.format (23.123123));/* * Result: * 23,123,123 * 23,123.123 * 23.123 * */}}
DecimalFormat
As with Simpdateformat, you can specify the format to display:
Import Java.text.decimalformat;class demo{String p;DoubleN Public Demo(String p,DoubleN) {//Initialize This. p = p; This. N = n; } Public void format(){//Get formatDecimalFormat format =NewDecimalFormat (P);//Formatted outputSystem. out. println (Format.format (n)); }} Public classDemo1 { Public Static void Main(string[] args) {//TODO auto-generated method stub NewDemo ("000,000.00",2345.326). Format ();NewDemo ("###,000.00",2345.326). Format ();NewDemo ("# #0, 000.00¥",2345.326). Format ();NewDemo ("###,000.00%",2345.326). Format (); }}
Description of related symbols:
BigInteger, BigDecimal
Import Java. Math. BigDecimal;Import Java. Math. BigInteger;public class Demo1 {public static void main (string[] args) {//instancing large number BigInteger i = new BigInteger ("0");Instantiate a large number of floating-point BigDecimal j = new BigDecimal ("7654321");BigDecimal k = new BigDecimal ("1234567");System. out. println("i="+i);System. out. println("j="+J);System. out. println("k="+K);System. out. println("Addition"+j. Add(k));System. out. println("Subtraction"+j. Subtract(k));System. out. println("Multiplication"+j. Multiply(k));System. out. println("Division"+j. Divide(k));Bigdecimal[] result = J. Divideandremainder(k);//retention quotient and remainderSystem. out. println("Business"+result[0]+", remainder"+result[1]);}}
Common library of Basic Java Knowledge (2)