*3.18（运输成本）一个运输公司使用下面的函数，根据运输重量（以磅为单位）来计算运输成本（以美元计算）。
编写一个程序，提示用户输入包裹重量，显示运输成本。如果重量大于20，显示信息“the package cannot be shipped”。如果重量等于或者小于0，则显示信息“Invalid input”。
*3.18(Cost of shipping) A shipping company uses the following function to calculate the cost (in dollars) of shipping based on the weight of the package (in pounds).
Write a program that prompts the user to enter the weight of the package and display the shipping cost. If the weight is greater than 20, display a message “the package cannot be shipped.”
参考代码：
方法一：package chapter03; import java.util.Scanner; public class Code_18 { public static void main(String[] args) { double weightOfShip; // Prompt the user to enter the weight of the package System.out.print("Enter the weight of the package(in pounds): "); Scanner input = new Scanner(System.in); weightOfShip = input.nextDouble(); // Display the cost of shipping and other situation if(weightOfShip > 0 && weightOfShip <= 1) System.out.println("The cost of shipping is 3.5"); else if(weightOfShip > 1 && weightOfShip <= 3) System.out.println("The cost of shipping is 5.5"); else if(weightOfShip > 3 && weightOfShip <= 10) System.out.println("The cost of shipping is 8.5"); else if(weightOfShip > 10 && weightOfShip <= 20) System.out.println("The cost of shipping is 10.5"); else if(weightOfShip <= 0) System.out.println("Invalid input"); else if(weightOfShip > 20) System.out.println("The package cannot be shipped"); input.close(); } } 方法二：package chapter03; import java.util.Scanner; public class Code_18another { public static void main(String[] args) { double costOfShip = 0,weightOfShip; // Prompt the user to enter the weight of the package System.out.print("Enter the weight of the package(in pounds): "); Scanner input = new Scanner(System.in); weightOfShip = input.nextDouble(); // Display the cost of shipping and other situation if(weightOfShip > 0 && weightOfShip <= 1) costOfShip = 3.5; else if(weightOfShip > 1 && weightOfShip <= 3) costOfShip = 5.5; else if(weightOfShip > 3 && weightOfShip <= 10) costOfShip = 8.5; else if(weightOfShip > 10 && weightOfShip <= 20) costOfShip = 10.5; else if(weightOfShip <= 0) System.out.println("Invalid input"); else if(weightOfShip > 20) System.out.println("The package cannot be shipped"); if(costOfShip != 0) { System.out.println("The cost of shipping is " + costOfShip); } input.close(); } }结果显示：
Enter the weight of the package(in pounds): 2 The cost of shipping is 5.5 Process finished with exit code 0