JavaSE class record (b)

the first lesson

Overloaded methods: the same method name, a list of different parameters
Rewrite method: method name, same parameter list
1. Two same: the same method name, same parameter list
2. Two small: small and equal access to the parent class, the type of the return value less than or equal parent (the return value of basic data types, must be equal, it must be less than or equal parent class reference data type)
3. A large: greater than or equal to the thrown exception parent

For ease of use and maintenance, the subcontracting, the JDK class library is divided in accordance with the packet structure, different functions divided in different packages. The package is often used as follows:

package	Features
java.lang	Base class java program, such as a string, multithreaded, java.lang class uses the higher frequencies, it can be used directly
java.util	Conventional tools, such as the collection, Random
java.io	File operations, input and output
java.net	Network-related operations
java.math	Math-related operations
java.security	Security-related actions
java.Text	Processing text, date, number, format and other operations.

Documentation Comments
1. With / ** start / end
2. see See, author of, since began;
Scanner class
1. The step of using the reference package
  1. import package name. Class name
  2. For example:
  3. ```
   import java.util.Scanner 
```
2. Create Object
  1. Creating an object using the constructor method of the class
    1. format:
    2. ```
     Data type variable name = new new data type (parameter list); // example Scanner SC = new new Scanner (the System.in); 
```
3. Call the method
  1. ```
   int I = scan.nextInt (); // . Variable Name Method Name 
```
4. Receiving a string
  1. 　　
```
scan.next();      
scan.nextLine();
```
    　　
5. the difference:
  1. The next method is effective to meet the first character (non-spacing, line breaks) to start scanning, when encountering the first space or end delimiter, end of the scan
  2. nextLine () method is to scan a single line.