Java console input streams System.in and Scanner

System.out is commonly used to output data in the console
System.in can input data from the console

Step 1: system. In

package stream;
 
import java.io.IOException;
import java.io.InputStream;
 
public class TestStream {
 
    public static void main(String[] args) {
        // Console input 
        try (InputStream is = System.in;) {
            while (true) {
                // Tap in a, then tap back to see
                // 97 13 10
                // 97 is the ASCII code of a
                // 13 10 corresponding to carriage return
                int i = is.read();
                System.out.println(i);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Step 2: scanner reads the string

Although System.in.read can read data, it is not convenient
With Scanner, you can read line by line

package stream;
    
import java.util.Scanner;
    
public class TestStream {
    
    public static void main(String[] args) {
         
            Scanner s = new Scanner(System.in);
             
            while(true){
                String line = s.nextLine();
                System.out.println(line);
            }
         
    }
}

Step 3: scanner reads integers from the console

Using Scanner to read integers from the console

package stream;
 
import java.util.Scanner;
 
public class TestStream {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        int a = s.nextInt();
        System.out.println("First integer:"+a);
        int b = s.nextInt();
        System.out.println("Second integer:"+b);
    }
}

Practice: Auto create class

Automatically create a class file with one property.
Through the console, get the class name, property name and property type. According to a template file, create the class file automatically, and provide setter and getter for the property

public class @class@ {
    public @type@ @property@;
    public @class@() {
    }
    public void set@Uproperty@(@type@  @property@){
        this.@property@ = @property@;
    }
      
    public @type@  get@Uproperty@(){
        return this.@property@;
    }
}

Answer:

package stream;
 
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;
 
public class TestStream {
 
    public static void main(String[] args) {
        // Accept customer input
        Scanner s = new Scanner(System.in);
        System.out.println("Please enter a name for the class:");
        String className = s.nextLine();
        System.out.println("Please enter the type of property:");
        String type = s.nextLine();
        System.out.println("Please enter the name of the property:");
        String property = s.nextLine();
        String Uproperty = toUpperFirstLetter(property);
         
        // Read template file
        File modelFile = new File("E:\\project\\j2se\\src\\Model.txt");
        String modelContent = null;
        try (FileReader fr = new FileReader(modelFile)) {
            char cs[] = new char[(int) modelFile.length()];
            fr.read(cs);
            modelContent = new String(cs);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }      
         
        //replace
         
        String fileContent = modelContent.replaceAll("@class@", className);
        fileContent = fileContent.replaceAll("@type@", type);
        fileContent = fileContent.replaceAll("@property@", property);
        fileContent = fileContent.replaceAll("@Uproperty@", Uproperty);
        String fileName = className+".java";
         
        //Replaced content
        System.out.println("Replaced content:");
        System.out.println(fileContent);
        File file = new File("E:\\project\\j2se\\src",fileName);
 
        try(FileWriter fw =new FileWriter(file);){
            fw.write(fileContent);
        } catch (IOException e) {
            e.printStackTrace();
        }
         
        System.out.println("File saved in:" + file.getAbsolutePath());
    }
     
    public static String toUpperFirstLetter(String str){
        char upperCaseFirst =Character.toUpperCase(str.charAt(0));
        String rest = str.substring(1);
        return upperCaseFirst + rest;
         
    }
}