Java basics and java tips

Java basics and java tips

I have never written a blog before. Now I start to review and remember some easy-to-Forget tips.

One java retains two decimal places

1> BigDecimal Method

Double f = 11.3156;

BigDecimal B = new BigDecimal (f );

F = B. setScale (2, BigDecimal. ROUND_HALF_UP). doubleValue ();

2> DecimalFormat format

Double f = 11.3156;

DecimalFormat df = new DecimalFormat ("#. 00 ");

Df. format (f );

3> String method

Double f = 11.3156;

String s = String. format ("%. 2f", f );

F = Double. valueOf (s );

2. Four ways to create an object

1> new 2> reflection mechanism 3> Object stream 4> clone

Three-time Conversion

Date date = new Date ();

SimpleFormat sdf = new SimpleFormat ("yyyy-MM-dd HH: mm: ss ");

String s = sdf. format (date );

Date as = sdf. parse (s); // throw ParseException