JAVA based learning (6) of using objects

6 Using Objects

• 6.1 Character Types
  • 6.1.1 Character Types
    • int char and convert each

    • 1 //a比A大32
      2         Scanner in=new Scanner(System.in);
      3         char c='B';
      4         char c1=(char)(c+'a'-'A');
      5         System.out.println(c1);

       

  • 6.1.2 Escape character
    • Special characters
• 6.2 Package Type
  • 6.2.1 Package Type
    • 　　

       1 public static void study25()//6.2.1
       2     {
       3         System.out.println(Integer.MAX_VALUE);
       4         System.out.println(Integer.MIN_VALUE);
       5     }
       6     
       7     public static void study26()//6.2.1
       8     {
       9         System.out.println(Character.isLowerCase('a'));
      10         System.out.println(Character.toLowerCase('B'));
      11     }
      12     
      13     public static void study27()//6.2.1
      14     {
      15         System.out.println(Double.MAX_VALUE);
      16     }
      17     
      18     public static void study28()//6.2.1
      19     {
      20         boolean b=false;
      21         System.out.println(Boolean.toString(b));
      22     }

       

  • 6.2.2Math class
    • abs
    • pow
    • random
    • round

    • 1 System.out.println(Math.abs(-1));
      2         System.out.println(Math.round(11.545));
      3         System.out.println(Math.random());
      4         System.out.println(Math.pow(2, 3.6));

       

• 6.3 String
  • 6.3.1 string variable
    • 　　

      Scanner in=new Scanner(System.in);
              S String = new new String ();
       //         S = in.next (); // read a word
       //         System.out.println (+ 24 + 12 is S); 
              S = in.nextLine (); // read the entire row 
              System.out.println (s);

       

    • Scanner in=new Scanner(System.in);
              A String = new new String ( "Hello"); // first String object 
              String A = B; // management objects assigned 
              System.out.println (b);
              B = "Hello"; // Second String object 
              System.out.println (a);
              System.out.println(b);
              System.out.println (a.equals (B)); // String equal need equals

       

  • 6.3.2 String operations
    • 　　

      . 1 String A = "ABC" ;
       2          String B = "ABD" ;
       . 3          
      . 4          System.out.println (a.compareTo (B)); // size comparison 
      . 5          System.out.println (a.charAt (2)) ; // output character specified position 
      . 6          System.out.println ( "012345" .substring (2,4)); // output sub-string 
      . 7          System.out.println ( "012345" .substring (2 ));
       . 8          System.out.println ( "012345" .substring (2 ));