java 定时程序扫描表_Java扫描程序类

╰半橙微兮° 2023-02-28 08:41 2阅读 0赞

java 定时程序扫描表

Scanner class in Java (`java.util.Scanner`) was introduced in Java 1.5 as a simple text scanner which can parse primitive types and strings using regular expressions.

Java 1.5中引入了Java的Scanner类（ `java.util.Scanner` ），它是一种简单的文本扫描程序，可以使用正则表达式解析原始类型和字符串。

## Java扫描程序类 **(****Scanner Class in Java****)** ##

Java Scanner class can be used to break the input into tokens with any [regular expression][] delimiter and it’s good for parsing files also.

Java Scanner类可用于使用任何[正则表达式][regular expression]定界符将输入分解为令牌，这对于解析文件也非常有用。

Scanner class can be used to read file data into primitive. It also extends String *[split()][split]* method to return tokens as String, int, long, Integer and other wrapper classes.

扫描程序类可用于将文件数据读取为原始数据。 它还扩展了String *[split（）][split]*方法，以将令牌作为String，int，long，Integer和其他包装器类返回。

## Java扫描仪示例 **(****Java Scanner Example****)** ##

Here I am using Scanner to read a file line by line, parsing a CSV file to create java object easily and read from the user input.

在这里，我使用Scanner逐行读取文件，解析CSV文件以轻松创建java对象并从用户输入中读取。

`JavaFileScanner.java`

package com.journaldev.files;
    
    import java.io.IOException;
    import java.nio.file.Path;
    import java.nio.file.Paths;
    import java.util.Scanner;
    
    public class JavaFileScanner {
    
        public static void main(String[] args) throws IOException {
            /**
             *  My Name is Pankaj
             *  My website is journaldev.com
             *  Phone : 1234567890
             */
            String fileName = "/Users/pankaj/source.txt";
            Path path = Paths.get(fileName);
            Scanner scanner = new Scanner(path);
            
            //read file line by line
            scanner.useDelimiter(System.getProperty("line.separator"));
            while(scanner.hasNext()){
                System.out.println("Lines: "+scanner.next());
            }
            scanner.close();
            //read CSV Files and parse it to object array
            /**
             * Pankaj,28,Male
             * Lisa,30,Female
             * Mike,25,Male
             */
            scanner = new Scanner(Paths.get("/Users/pankaj/data.csv"));
            scanner.useDelimiter(System.getProperty("line.separator"));
            while(scanner.hasNext()){
                //parse line to get Emp Object
                Employee emp = parseCSVLine(scanner.next());
                System.out.println(emp.toString());
            }
            scanner.close();
            
            //read from system input
            System.out.println("Read from system input:");
            scanner = new Scanner(System.in);
            System.out.println("Input first word: "+scanner.next());
        }
        
        private static Employee parseCSVLine(String line) {
             Scanner scanner = new Scanner(line);
             scanner.useDelimiter("\\s*,\\s*");
             String name = scanner.next();
             int age = scanner.nextInt();
             String gender = scanner.next();
             JavaFileScanner jfs = new JavaFileScanner();
             return jfs.new Employee(name, age, gender);
        }
    
        public class Employee{
            private String name;
            private int age;
            private String gender;
            
            public Employee(String n, int a, String gen){
                this.name = n;
                this.age = a;
                this.gender = gen;
            }
            
            @Override
            public String toString(){
                return "Name="+this.name+"::Age="+this.age+"::Gender="+this.gender;
            }
        }
    
    }

Output of the above program is:

上面程序的输出是：

Lines: My Name is Pankaj
    Lines: My website is journaldev.com
    Lines: Phone : 1234567890
    Name=Pankaj::Age=28::Gender=Male
    Name=Lisa::Age=30::Gender=Female
    Name=Mike::Age=25::Gender=Male
    Read from system input:
    Pankaj Kumar
    Input first word: Pankaj

We can use java Scanner class to parse the input into specific datatype tokens.

我们可以使用java Scanner类将输入解析为特定的数据类型标记。

Read this post to learn [how to read CSV File using Scanner][].

阅读这篇文章，了解[如何使用Scanner读取CSV文件][how to read CSV File using Scanner] 。

Reference: [API Doc][]

参考： [API文档][API Doc]

> 翻译自: [https://www.journaldev.com/872/scanner-class-in-java][https_www.journaldev.com_872_scanner-class-in-java]

java 定时程序扫描表

[regular expression]: https://www.journaldev.com/634/regular-expression-in-java-regex-example
[split]: https://www.journaldev.com/791/java-string-split
[how to read CSV File using Scanner]: https://www.journaldev.com/2335/read-csv-file-java-scanner
[API Doc]: https://docs.oracle.com/javase/10/docs/api/java/util/Scanner.html
[https_www.journaldev.com_872_scanner-class-in-java]: https://www.journaldev.com/872/scanner-class-in-java