JAVA learning (two) ----- useful in java programming package | method | Usage

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• INPUT LIST:
  . * Classes in java.util
  Scanner Scanner new new SC = ( the System.in );
  int sc.nextInt A = ();

• Random number to call:

1. . * the java.lang
   the Random new new RD = the Random ();
   int = A rd.nextInt (20 is) +5; // randomly generates a random number of 5-25
   int b = rd.nextInt (9) * 10 + rd.nextInt (9);

2. Math.randow (); 0-1 random number (including 0 1 not included)
   , for example: (int) (Math.randow () 10); // random number 0-10
   min Math.randow + () (min-max ); // min-max nonce

• Call control decimal digits (rounded):
  . * The java.lang
  Classes in java.math *.
  Double F = (9.0 /. 5) * 32 + Celsius;
  Double the BigDecimal new new F1 = (F) .setScale (. 1, BigDecimal.ROUND_HALF_UP). doubleValue ();
  return f1; // one decimal (rounded)

• Acquisition system timestamp: (1970 to date)
  System.currentTimeMillis (); // Get System milliseconds
  System.nanoTime (); // Get System nanoseconds

• Math function in
  Math.pow (); a power of
  the Math.abs (); absolute value
  Math.ceil (); rounding up (take 3.1. 4)
  Math.floor (); rounded down (get 3 3.1)

• Input character
  char c = sc.next () charAt ( 0).;

• The positive numbers into a string
  String name = String.ValueOf (Integer Name); egg: String s = String.ValueOf (num);

• Equal to the comparison string (not ==)
  String Next opt = ();
  IF ( "+" the equals (opt).)

• String inverted
  StringButter sb = new StringButter (str) ; // the string str inverted
  sb.reverse ();
  String str1 = new new String (SB);

• Dividing the capacity of a string of a string (the string divided) (a string STR, str1 array of strings)
  String [] Name = Original name .split ( ""); egg: String [] str1 = str .split ( "");