The basic class library is a class library provided by java. When we develop, we can select classes from the library and call its methods to implement some functions.
Free video tutorial recommendation:java teaching video
For example:
(1) Scanner
Scanner can read user keyboard input and file input.
//System.in代表键盘输入 Scanner sc=new Scanner(System.in); //增加下面一行将只把回车作为分隔符 sc.useDelimiter("\n"); //判断是否还有下一个输入项 while(sc.hasNext()) { //输出输入项 System.out.println("键盘输入的内容是:"+sc.next()); }
(2) System
The methods in the System class are:
1. Access the environment variables and system properties of the platform where the program is located;
2. Get the current time of the system - currentTimeMillis(), nanoTime();
3. in, out, and err represent the standard input, standard output, and error output streams of the system respectively;
4. It can return the exact hashCode value of the specified object. If the identityHashCode value of two objects is the same, the two objects must be the same object - identityHashCode(Object x);
(3) Runtime
The methods in the Runtime class are:
1. Notify the system to perform garbage collection and clean up system resources - gc(), runFinalization()
2. Load files and dynamic link libraries - load(), loadLibrary()
3. Access JVM related information, such as the number of processors, memory information, etc. ——availableProcessors(), totalMemory()
4. Directly start a separate process to run the operating system
Recommended related articles and tutorials:java quick start
The above is the detailed content of What is the basic class library in java?. For more information, please follow other related articles on the PHP Chinese website!