java - 对文本文件中的值求和并打印它们

Question

这个问题已经有答案了:

Java arrays printing out weird numbers and text [duplicate] (10 个回答)

How do I print my Java object without getting "SomeType@2f92e0f4"? (14 个回答)

已关闭 5 年前。

我正在尝试从文本文件添加书籍的成本并打印它们。但是，我得到 [Ljava.lang.Double;@55f96302我的值(value)观应该在哪里。

这是我当前的代码:

System.out.println("Welcome to the libary book search system.");
System.out.println("------------------------------------------");

if(choice.equals("Text File")) {

    //String sc = null; 
    System.out.println("Title\t\t\tAuthor\t\t\tPrice\t\t\tBookPublisher\t\t\tISBN");
    System.out.println("=====\t\t\t======\t\t\t=====\t\t\t=============\t\t\t====");

    int count = 0;

    try {
        File Fileobject = new File ("E:\\text files for java\\BooksToImport.txt");
        Scanner sc = new Scanner(Fileobject);

        // Read and display each line of the file
        while(sc.hasNextLine()) {
            String line2 = sc.nextLine();
            Scanner sc2 = new Scanner(line2);
            sc2.useDelimiter("-");
            System.out.println(line2);

            while(sc2.hasNext()) {
                BookTitle[count] = sc2.next();
                System.out.println(BookTitle[count]);
                BookAuthor[count] = (sc2.next());
                System.out.println(BookAuthor[count]);
                BookPrice[count] = sc2.next();
                System.out.println(BookPrice[count]);
                BookPublisher[count] = sc2.next();
                System.out.println(BookPublisher[count]);
                ISBN[count] = sc2.next();
                System.out.println(ISBN[count]);
            }

            sc2.close();
            count++;

        }       

        //for(int index=0;index<count;++index) {
            //BookPrice2[index]=Double.parseDouble(BookPrice[index]);
            //System.out.println(BookPrice2[index]);
        //}

        sc.close();         
        System.out.println("----------------------");   
        System.out.println("Totals of the Text File:");
        System.out.println("----------------------");
        System.out.println("Total Numbers Of Books:" + NUMBEROFBOOKS);
        System.out.println("Total Cost Of Books:"+ BookPrice2 );
        System.out.println("Maximum Cost Of A Book:"); 
        System.out.println("Minimum Cost Of A Book:");
        System.out.println("Average Cost Of A Book:"); 
        System.out.println("Total number of valid books:"); 
        System.out.println("Total number of invalid books:"); 
    } catch (FileNotFoundException e) {
            System.out.println("File does not exist");
    }
}

这是我的文本文件:

The Hunger Games - Suzanne Collins - 5 - Scholastic Press - 9781921988752
OOP programming - Graham Winter - 32 - Oriely - 9876543219
Harry potter - Jk Rowling - 10 - Bloomsbury - 9788700631625

这是我的 java 程序显示的内容:

Enter what you want to do: Type 'Input' for user input or 'Text File' to read from file.

Text File

Welcome to the libary book search system.
------------------------------------------
Title           Author          Price           BookPublisher               ISBN
=====           ======          =====           =============           ====
The Hunger Games - Suzanne Collins - 5 - Scholastic Press - 9781921988752
The Hunger Games 
Suzanne Collins 
5 
Scholastic Press 
9781921988752
OOP programming - Graham Winter - 32 - Oriely - 9876543219
OOP programming 
Graham Winter 
32 
Oriely 
9876543219
Harry potter - Jk Rowling - 10 - Bloomsbury - 9788700631625
Harry potter 
Jk Rowling 
10 
Bloomsbury 
9788700631625
----------------------
Totals of the Text File:
----------------------
Total Numbers Of Books:3
Total Cost Of Books:[Ljava.lang.Double;@55f96302
Maximum Cost Of A Book:
Minimum Cost Of A Book:
Average Cost Of A Book:
Total number of valid books:
Total number of invalid books:

Answer 1

java.lang.Double@55f96302 的当前输出是 Double 包装类的 toString() 输出，该类继承了 Object 类的 toString() 方法。您看到的值是该对象的内存地址。

并且您想输出该值的字符串表示形式。为此，您可以使用 Double 的 doubleValue() 方法将对象转换为原始类型:double。

在此处使用BookPrice2.doubleValue():

System.out.println("书籍总成本:"+ BookPrice2.doubleValue() );//+ gb.format());

旁注:Java 中的变量名称应以小写字母开头，因此 BookPrice2 应命名为 bookPrice2。随着您继续学习 Java，您将学到更多命名约定。