Java differs from C + + programming

1. Data types and variables

Variable types in C + + are similar to Java. Like Java, C + + has int and double types. However, the range of values for these numeric types is dependent on the machine. For example, on a 16-bit system, such as a PC running DOS or Windows 3.x, int is a double-byte (2-byte), and the value range is much smaller than that of the Java 4-byte Int. On these machines, if int is not enough, you need to use a long integer.

C + + has the short and unsigned types to more efficiently store numbers. (I think the so-called effective means higher space utilization.) It is best to avoid using these types unless the effectiveness of space use is really important to your system.

Boolean in C + + is represented in bool, not as Boolean in Java.

The string type in C + + is represented by a string. It's very similar to the string type in Java, but there are a few different ways to do this:

1.c++ strings store ASCII characters instead of standard code Unicode characters

The 2.c++ string can be modified, while the contents of the Java string are not modifiable (immutable).

3. The operation of the substring is called substr in C + +, and this command s.substr (i, N) obtains from the string s a substring from position I from the length of N.

4. In C + +, you can only concatenate strings with other string objects (concatenate) without being able to concatenate with any object.

5.c++ can be used to compare strings directly using the relational operator = =,!=, <, <=, >, >=, where four operators are compared in alphabetical order. This is much more convenient than using the function equals and CompareTo in Java.

2. Variables and Constants

In C + +, the definition of a local variable looks the same as in Java, for example:

int n = 5;

This is actually one of the important differences between C + + and Java. The C + + compiler does not initialize local variables, so it is easy to forget to initialize a variable in C + +, in which case the value of the variable has exactly the current random value in the memory area. This is obviously a very easy place to create a program error.

As with Java, classes in C + + can have data fields and static variables. The difference is that variables in C + + can be defined outside of a function or even a class, and these so-called global variables can be accessed in any function of the program, and thus are not easily managed properly. You should try to avoid using global variables in C + +.

In C + +, constants can be defined anywhere (remember that in Java, constants must be static data for a class). C + + uses the keyword const to define constants, which are final in Java. For example:

const int days_per_year = 365;