包装和扫描仪类Java中

Question

这些是分配的说明：

For this Question, you will be using two of the prominent wrapper classes to convert String variables 
    which represent numerical data into primitive types as instances of the wrapper classes. 
    As part of this Question you will be using a Scanner object to read in user input. 
    There are also 2 previously declared and instantiated String object references, value1 and value2 
    that you will use as part of this exercise. 

    1) Declare an int variable with the identifier parsedInt, and double variable with the identifer parsedDouble 
    2) Use a static method of the Integer class to convert the String object reference value1 to an int 
     and assign that value to the parsedInt variable. 
    3) Use a static method of the Double class to convert the String object reference value2 to a double 
     and assign that value to the parsedDouble variable. 
    4) Declare 2 Double variables with identifiers of your choosing. 
    5) Declare an instantiate a Scanner variable (object reference) with the identifier of your choosing 
     Make sure that it can read from the Java console (System.in) and that you have imported the Scanner class 
    5) Using a static method of the Double class, convert String values read in from the console 
     (by calling the nextLine method on your Scanner object reference) to the Double type 
     and assign them to the two Double object references declared in the previous step. 
    6) Declare 2 boolean variables with the identifiers isInfinite and isNaN 
    7) Call methods on your Double object references to make the following tests and store the result in the proper variable 
     Use a method to test if the first value that you read in from the console is Infinite 
     Use a method to test if the second value that you read in from the console is Not a Number (NaN) 
    8) Declare an int variable result 
    9) Convert the values of the two Double object references to integers 
     and subtract the second number that was read in from the first that was read in 
     and assign the result of that mathematical expression to the variable result 

我的问题在5号开始，我不太清楚，我被要求做，我不知道如何将字符串值转换为双打。这是我到目前为止有：

double woof1, woof2; 
    boolean isInfinite, isNaN; 
    int result; 

    Integer parsedInt = new Integer(value1); 
    Double parsedDouble = new Double(value2); 

    Scanner scan = new Scanner(System.in); 

更新 现在我有这个

double woof1, woof2; 
    boolean isInfinite, isNaN; 
    int result; 

    Integer parsedInt = new Integer(value1); 
    Double parsedDouble = new Double(value2); 

    Scanner scan = new Scanner(System.in); 

    woof1 = Integer.parseInt(scan.nextLine()); 
    woof2 = Double.parseDouble(scan.nextLine()); 

，现在我不知道该怎么办7号

Answer 1

首先 - 你已经得到了扫描仪的参考。这是一个开始，但我建议您在声明任何其他数字类型之前。

二 - 所有的数值包装，如Integer，Long，和Double支持parse###方法，包括他们正在解析基本类型的名称。他们以String作为他们的正式论点。例如，对于Integer包装器，其解析方法是Integer.parseInt()。

第三，从Scanner实例中读取一条线就像scan.nextLine()一样简单。如果该行包含要解析的数字，并且您想解析Double，请考虑实际上是什么Double.parse###。我把这个作为练习留给读者。

Answer 2

根本就

double parsedDouble = Double.parseDouble(scan.nextLine()); 

但是，这是一个愚蠢的问题b因为它会更好做

double parsedDouble = scan.nextDouble();