This week, we insist on learning every day Java requires one hour to learn java to build and run the application development environment (previously the students to help build configuration) to re-install the independent Eclipse familiar with the Eclipse working directory and use this compiler written some simple little program.
First, learn java and c / c ++ something different:
Java. 1 , can not be outside the class definition of global variables, global variables can only be achieved by defining a common, in a static class variable. E.g:
class A{
public static a; // the class A is defined in a as public static, so that other classes can access and modify this variable.
}
2 Java is a dynamic memory allocation , which uses object-oriented mechanism , using the operator new to allocate memory space for each object , and , the actual program memory also vary with operating conditions . Program is running , each , Java system automatically scans memory , spatial long as no "junk" collected , making the system more fully utilize the resources . in this mechanism , the programmer need not be concerned about memory management issues , which makes the Java programming becomes simple , and avoids errors due to memory management system and cause problems . the C language by malloc () and free () these two library functions to achieve the allocation and release of internal memory respectively , C ++ language in the by operators new and deleteTo allocate and free memory . In C and C ++ This secondary mechanism , the programmer must deal with the use of memory very carefully . On the one hand , if the memory of the already released or re-released as a memory for the release has not been allocated , will result in crashes ; on the other hand , if you do not release the memory no longer in use or long-term unused , will be a waste of system resources , even thus causing resource depletion .
3 Java do not goto statement , but with the try-catch-finally exception handling statement instead goto statements to handle error function .
4 Java does not support the header files , face C and C ++ language are used to define a class prototype header file , global variables , library functions and the like , such a structure makes use of header files maintenance of the system very complicated operation .
5 Java does not support macros , but the use of the keyword final to define constants , in C ++ in the use of macro definitions to achieve constant definitions , which may not in readability .
Java. 6 for each data type is assigned a fixed length . For example , in Java in , int type is always 32 bits , while in C and C ++ in , for different platforms , with a different type of data the number of bytes allocated , equally is int type , the PC machine is two bytes i.e., 16 bit , and the VAX-11 medium , compared to 32 bit . this makes the C language without causing portability , but Java is having a cross-platform ( platform independence ).
7 different types of conversion . In C and C ++ in , can be arbitrarily switched by a pointer type , often bring insecurity , in Java in , run-time processing system of the object to be compatible with the type of examination , in order to prevent safety conversion .
8 structure and processes combined . In C and C ++ in , structure and all members of the union are public , which has brought security issues , and in Java in simply do not include structures and unions , all content is encapsulated in class inside
9 Java is no longer using the pointer . Pointer is a C and C ++ is the most flexible , and most error-prone data type . Memory address operations carried out by the pointer often cause unpredictable errors , at the same time significantly for a memory address refers to after casts , can access a C ++ the private members , thereby undermining security . and Java pointer is fully controlled , the programmer can not make any direct pointer operation .
Second, watched javaweb WEB02_HTML & CSS video to explain, learn Javascript regular and table expression (regular expression is defined, the regular expression associated with a string object methods) but did not fully understand, so do not press last week plans to continue learning WEB03_JavaScript, but repeated learning WEB02_HTML & CSS deepen understanding.
Third, read the "Road to Jane," the second chapter is lazy created a method, by contrast Yu Gong Li Bing and understand a person's energy, after all, there is a limit. The proposed new "approach" to address the fundamental problems affecting the work would be fruitful. After talking about the subject from the little things in life inspiration: they had learned about the classification, summarize, neatly placed on his head. So you know what is the knowledge learned. Second, we know the essence of the program: Program = algorithm + data + methods. And in learning to think more about not just keep knocking the code, do problems.
Fourth, the next week plan:
1, learning java Chapter VI of objects, classes, packages and interfaces. And the java programming 2017 before the commencement of the examination of student information management.
2, learning WEB03_JavaScript, and recalled the first two weeks learning content.
3, read the "Road to Jane," the third chapter.