shhgs@wgqqh.com 




     2002      7 
    chinapub 




                   8 
                                                   Bruce Eckel 


                           1000     ) 
                                                                7 
                                                                       - 


                                                                    + 2 

       Bruce Eckel                         1000     ) 
                                                                             The 
genesis of the computer revolution was in a machine. The genesis of our 
programming languages thus tends to look like that machine. 
                                          Bruce 




                 10                          7 

                         www.wgqqh.com/shhgs/tij.html 




                                                                              shhgs 

                                                                   2003     9     8 
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2: 
      Java          C+ + 


C+ +      Java                    Java 
                                                   
C+ +C+         C+ + 
                                         / 
       + C                        C+ +      C     C 



Java                                                           / 
                                      (     O O P          ) 


      Java              Java            Java 

    reference 

                                                    / 
      (     C    C+ +        ) 
Java 


(reference)    reference     ¤ 
                     (     )              reference 

            reference       /reference 
                                                    reference 

String      reference 

        String s; 




                          reference                s              s 

              (          )       (             )     reference 


        String s = "asdf"; 
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                Java 
                                    / 

      / 
ne w    reference                 ne w 


     String s = new String("asdf"); 




                  String       String 


     String                     Java   Java 




                                ü ü 

1.         (registers) 



2.    (stack)                    (general random-access memory area) 
                        (stack pointer) 

                                            Java           / 
                           / 
                  Java             ü ü 
                                                    reference 

3.    (heap)                                 (general-purpose pool of 
    memory               )            Java 



                  new 


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                                                                                                                                         ( 
                             C++                                                                   ) 
4.                          (static storage) 
            (                               RAM                           ) 
                                                                    static 
                             Java 
5.                          (constant storage) 

                                                                                                         ROM 
6.                                     (Non-RAM storage) 

                                                                                                  (streamed object)                 persistent 
                    (persistent object) 




                        Java                                                  persistence (lightweight persistence) 
                             Java                                                            persistence 

              :     p  r i m i t i v e 



ne w               p ri m i ti ve(             ) 
                                ü ü 
                                                                                                        Java                 C       C+ + 

                              reference                                            ne w 



Java                                  p ri m i ti ve                                                      Java 


 bcbshohy oarrtane 
    P rim itiv                                                                                                                    e 
               l e                      —                                                                           W rapl panr 
                                                                                                                          o e 

           ote                          8-b                       -128   §§              + 127                           hoy arac 
                                       162-b                     -2§§ —1           +++IEIE 2E2E                          teo rt 
 intng                                                                                       2                                      r 
 lfd ol                                     4-b                   -2¨¨ —1 
                                                                -2            d e 0 U—ni co d e 2§¨ - 1 CBBShntengge te r 
                                                                                                     —1 
         oo uatb l e                    16 -bi-b itiiiii tttttt U—niEE coEE 
                                       3636 2-b 
                                           4-b                   IEIE        77 54 
                                                                              54                 EE 77 54 
                                                                                                      54        ILFD  oloo    uatl e 
                                                                                                                            b 

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     v o id                  —      —              —                         V o id 

                                                            u ns i g ned 
  (l i teral valou esl tru e o r f al se ) 
                 b   o e an                           tru e          f al se 


pP riri mm ii tve 
             ti ve           w rap p er              p ri m i ti ve 

               char c = 'x'; 
               Character C = new Character(c); 




               Character C = new Character('x'); 




  Java 
  B igD e c imp alm 
                  ri   i ti ve                                 B igIw nte geerr 
                                                                     rap p 



           B igI nte ge r      B igDp em c imti al 
                                    ri    i ve                  int       f l o at 



   B igI nte ge r 


   B igD e c im al 


                                                                             JD K 
    J a v a 
                                                 C    C+ +                        

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                                (                 ) 
            8 
     JavaJava                                 C     C+ + 
L 


 reference                                reference 
                                              l l 



     Java     referencereference 
                   Java       nu l l        nureference 
                                   / 
                nu l l 


          p ri m i ti ve 




      Java                                         b u g 
                                                       L 


        { }                   (s co p e)C C+ +      Java 


      { 
        int x = 12; 
        // Only x available 
        { 
          int q = 96; 
          // Both x & q available 
        } 
        // Only x available 
        // q “out of scope” 
      } 




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‘ //’ 
           Java                         Java 
Q 
                C    C+ +                                           Java 


         { 
           int x = 12; 
           { 
             int x = 96; // Illegal 
          } 
         } 




                 x             Java         C    C+ +Java 




  Java                   p ri m i ti ve                ne w      Java 


         { 
           String s = new String("a string"); 
         } // End of scope 




  s       reference                                   s            String 

                reference                                  reference 



           C+ +            ne w 
                                 L 
                                      Java                      C+ + 
               L 
                                               C+ + 



                         L 
                                      Java 

                    L 
  (gabage collector) 
     C+ +                                  ne w   Java 


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reference                 reference 



                       (m em o ry l eak )               L 

                                                                  ty p e 

            c l ass               c l ass 
                                      )              ( 


      class ATypeName { /* Class body goes here */ } 




  ne w )                               ( 




      ATypeName a = new ATypeName(); 




                                             )                       ( 




                     (Java       )                                    (f i eld 

m em ber f u n cti on )     )             (m eth od            reference 

reference       )                        p ri mreference ()ne 
                                              i ti ve 
                                                                  / 
                 (con s tru ctor              4 

  )                                                    (     w 

            (       p ri m i ti ve  reference                                   ) 




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         class DataOnly { 
            int i; 
            float f; 
            boolean b; 
         } 




         DataOnly d = new DataOnly(); 




                                                 / 
                 / 
                                     reference 


         objectReference.member 




         d.i = 47; 
         d.f = 1.1f; // ‘f’ after number indicates float 
         constant 
         d.b = false; 




         myPlane.leftTank.capacity = 100; 




 D ataO nl y 
                                      / 
 (retu rn v alu e)                                 (argu m en t) 


p rim itiv e 
   p ri m i ti ve 


                    bP orimo l e ane 
                                itiv 
                                          F al se 

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               cbshhy arrt 
                         ote                    ‘\ubshy 0000’ ( nu l l )