The main components and modules of the "Core" framework in the Java class library
The "Core" framework in the Java class library is the core part of the Java standard library. It contains many important components and modules, providing rich and powerful tools and functions for Java developers.In this article, we will introduce some of the main components and modules of the "Core" framework in the Java library, and provide related Java code examples to help readers better understand and use them.
1. Java.lang: This is the core package of the Java language, providing some basic classes and interfaces, such as Object, String, Integer, etc.It also provides classes and methods related to thread, abnormal processing and basic data type conversion.
Below is a simple example, showing the use of String in the java.lang bag::
public class Main {
public static void main(String[] args) {
String str1 = "Hello";
String str2 = "World";
System.out.println (str1.length ()); // Output: 5
System.out.println (str1.concat ("" " + STR2)); // Output: Hello World
System.out.println (str1.charat (2)); // Output: l
System.out.println (str1.indexof ("e"); // Output: 1
}
}
2. Java.util: This is a tool -like bag commonly used in the Java class library, which provides a variety of collection, dates and time, random number generators, regular expression matchmakers, etc.Its function is very rich and can be used to solve various common programming problems.
The following is an example that shows the use of the ArrayList class in the java.util package:
import java.util.ArrayList;
public class Main {
public static void main(String[] args) {
ArrayList<String> list = new ArrayList<>();
list.add("Apple");
list.add("Banana");
list.add("Orange");
System.out.println (list.get (1)); // Output: banana
System.out.println (list.size ()); // Output: 3
System.out.println (list.contains ("Grape"); // Output: false
System.out.println (list.indexof ("Orange"); // Output: 2
}
}
3. Java.io: This package provides classes and interfaces for processing and output, such as file reading and writing, flow operation, etc.It makes processing files and data flow simple and flexible.
The following is an example that shows the usage of FileInputStream and FileoutPutstream class in the java.io package:
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class Main {
public static void main(String[] args) {
try {
FileInputStream input = new FileInputStream("input.txt");
FileOutputStream output = new FileOutputStream("output.txt");
int data;
while ((data = input.read()) != -1) {
output.write(data);
}
input.close();
output.close();
System.out.println ("File replication is successful!"););
} catch (IOException e) {
e.printStackTrace();
}
}
}
In addition to the three components and modules mentioned above, the "Core" framework in the Java class library also contains many other important components, such as multi -threaded programming, network programming, graphic user interface (GUI) development, etc.These components and modules together constitute the core part of the Java library, providing rich and powerful functions and tools for Java developers.By making full use of the components and modules of the "Core" framework in the Java library, developers can develop and maintain the Java application more efficiently.
