使用异常验证输入

ve7v8dk2 于 2021-07-08 发布在 Java

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我是编程新手&我试着做一个算法来找出用户为每个科目输入的分数。在程序开始时，用户输入每个主题的所有标记。之后，电脑会自动按以下顺序打印所有的主题 subject - mark - grade .
我使用do while循环来避免用户输入超出范围的数字。另外，我想使用try-catch和do-while来避免从用户那里得到无效的变量类型。我把整个试接动作放到另一个边做边做的循环中。因此，它必须是循环的，直到用户在异常存在时输入一个整数值。但是当我输入了一个错误的变量类型 A 当程序运行时，计算机判定所有剩余的输入都是无效变量，没有用户的输入，并将所有这些“等级”的“标记”打印为零和空 >>Subject_4 - 0 - null . 否则，如果我输入一个正确的变量，它应该这样打印 >>Subject_1 - 56 - C . 我怎样才能解决这个问题？请帮帮我。

public class findResults {
int getMark;
int setMark;
String setGrade;
int arrayIndex;

String [] subjects = {"Subject_1","Subject_2","Subject_3","Subject_4"};
int [] marks = new int [subjects.length];
String[] grades = new String [subjects.length];

public findResults(){

    Scanner scan = new Scanner (System.in);
    System.out.println("Enter your marks for each subjects!");
    for (int t = 0;t<subjects.length;t++){
        arrayIndex = t;
        int x = 0;
    do{
        try {
            do{
                System.out.print(subjects[t]+" - ");
                getMark = scan.nextInt();
                setMark = ((getMark <= 100 && getMark >= 0)? getMark : (x=x-1));
                x = x+1;
            }while(x!=1);

        } catch (Exception e) {
            System.out.println("Please input valid number ..!");
    }
    }while(x!=x);

    }
    for (int i = 0; i<subjects.length;i++)
        System.out.println(subjects[i]+" - "+marks[i]+" - "+ grades[i]);
}
public void setResult(){
    if (setMark >= 75){
        setGrade = "A";
        marks[arrayIndex]= setMark;
        grades[arrayIndex]= setGrade;
    }
    else if(setMark >=65){
        setGrade = "A";
        marks[arrayIndex]= setMark;
        grades[arrayIndex]= setGrade;
    }
    else if(setMark >=65){
        setGrade = "B";
        marks[arrayIndex]= setMark;
        grades[arrayIndex]= setGrade;
    }
    else if(setMark >=55){
        setGrade = "C";
        marks[arrayIndex]= setMark;
        grades[arrayIndex]= setGrade;
    }
    else if(setMark >=35){
        setGrade = "S";
        marks[arrayIndex]= setMark;
        grades[arrayIndex]= setGrade;
    }
    else if(setMark >0){
        setGrade = "W";
        marks[arrayIndex]= setMark;
        grades[arrayIndex]= setGrade;
    }else{
        setGrade = "F";
        marks[arrayIndex]= setMark;
        grades[arrayIndex]= "Fail";
    }
}

}

Java variables Exception

来源：https://stackoverflow.com/questions/64859927/using-exception-for-validate-inputs

1条答案

按热度按时间

yc0p9oo01#

考虑以下几点。

private static String setGrade(int setMark) {
    String setGrade;
    if (setMark >= 75) {
        setGrade = "A";
    }
    else if (setMark >= 65) {
        setGrade = "B";
    }
    else if (setMark >= 55) {
        setGrade = "C";
    }
    else if (setMark >= 35) {
        setGrade = "S";
    }
    else if (setMark > 0) {
        setGrade = "W";
    }
    else {
        setGrade = "F";
    }
    return setGrade;
}

public static void main(String[] args) {
    String[] subjects = {"Subject_1", "Subject_2", "Subject_3", "Subject_4"};
    int[] marks = new int[subjects.length];
    String[] grades = new String[subjects.length];
    Scanner scan = new Scanner(System.in);
    System.out.println("Enter your marks for each subject.");
    for (int t = 0; t < subjects.length; t++) {
        System.out.printf("%s - ", subjects[t]);
        try {
            String str = scan.nextLine();
            marks[t] = Integer.parseInt(str);
            if (marks[t] < 0 || marks[t] > 100) {
                System.out.println("Between 0 and 100, please. Re-enter.");
                t--;
                continue;
            }
            else {
                grades[t] = setGrade(marks[t]);
            }
        }
        catch (NumberFormatException xNumberFormat) {
            System.out.println("Invalid value. Re-enter.");
            t--;
            continue;
        }
    }
    for (int i = 0; i < subjects.length; i++) {
        System.out.println(subjects[i] + " - " + marks[i] + " - " + grades[i]);
    }
}

下面是示例运行的输出。

Enter your marks for each subject.
Subject_1 - -2
Between 0 and 100, please. Re-enter.
Subject_1 - a
Invalid value. Re-enter.
Subject_1 - 10
Subject_2 - 90
Subject_3 - 4.3
Invalid value. Re-enter.
Subject_3 - 43
Subject_4 - 007
Subject_1 - 10 - W
Subject_2 - 90 - A
Subject_3 - 43 - S
Subject_4 - 7 - W

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使用异常验证输入

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