使用buffreader进行JAVA编程

Question

import java.io.*;  
public class Main {    
public static void main(String args[])throws Exception{             
     String MidtermLecGrade, MidtermLabGrade;
     String FinalLecGrade, FinalLabGrade;
     Float MG, temp;
     Float FG;
     Float Average;
     Float SemG;
     double a =0.6;
     double b = 0.4;



    BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
    System.out.print("Enter your Midterm Lecture Grade:");    
    MidtermLecGrade=br.readLine();
    System.out.print("Enter your Midterm Lab Grade:");    
    MidtermLabGrade=br.readLine();

    temp= (a * MidtermLecGrade) + (b*MidtermLabGrade);
    MG = Float.parseFloat(temp);
    System.out.println("Your Midterm Grade is :" + MG);

    }    
}   



error: bad operand types for binary operator '*'
        temp= (a * MidtermLecGrade) + (b*MidtermLabGrade);
                 ^
  first type:  double
  second type: String
 error: bad operand types for binary operator '*'
        temp= (a * MidtermLecGrade) + (b*MidtermLabGrade);
                                        ^
  first type:  double
  second type: String
 error: incompatible types: Float cannot be converted to String
        MG= Float.parseFloat(temp);


          ^

注意:一些消息已被简化；使用 -Xdiags:verbose 重新编译以获得完整输出

Answer 1

您需要将 a 和 b 变量转换为 float 。您还需要将用户输入解析为 float 。不需要其他变量。

public static void main(String args[]) throws Exception {
        String MidtermLecGrade, MidtermLabGrade;

        Float temp;
        float a = 0.6f;
        float b = 0.4f;

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Enter your Midterm Lecture Grade:");
        MidtermLecGrade = br.readLine();
        System.out.print("Enter your Midterm Lab Grade:");
        MidtermLabGrade = br.readLine();

        temp = ((a * Float.parseFloat(MidtermLecGrade)) + (b * Float.parseFloat(MidtermLabGrade)));
        System.out.println("Your Midterm Grade is :" + temp);

    }