Question

如何从传递的对象获取数组的大小。在下面的代码中，我创建了一个大小为10的对象，因为传递的Scanner对象有10行对象。但如果传递了100个物体呢？ 1000？怎么处理？例如：

public static Exam[] readAllExams(Scanner s) throws ArrayIndexOutOfBoundsException
    {

        String firstName = "";
        String lastName = "";
        int ID = 0;
        String examType = "";
        char examTypeCasted;
        int score = 0;

        int index = 0;

        Exam[] object = new Exam[10];

        while(s.hasNext())
        {
            //Returns firtsName and lastName 
            firstName = s.next();
            lastName = s.next();

            //Returns ID number
            if(s.hasNextInt())
            {
                ID = s.nextInt();
            }
            else 
                s.next();

            //Returns examType which is 'M' or 'F'
            examType = s.next();
            examTypeCasted = examType.charAt(0);

            if(s.hasNextInt())
            {
                score = s.nextInt();
            }

             object[index] = new Exam(firstName, lastName, ID, examTypeCasted, score);
            //System.out.println();
            index++;
        }
        readExam(s);
        return object;

Answer 1

使用动态增长的数据结构而不是数组：

ArrayList<Exam> object = new ArrayList<Exam>();

然后改变：

object[index] = new Exam(firstName, lastName, ID, examTypeCasted, score);

要：

object.add( new Exam(firstName, lastName, ID, examTypeCasted, score) );

您还需要将退货类型更改为ArrayList<Exam>，并且不要忘记导入它：

import java.util.ArrayList;

Answer 2

如果您无法使用ArrayList，则可以将代码更改为：

if (index == object.length) {
        Exam objectTmp[] = new Exam[object.length * 2];
        System.arraycopy(object, 0, objectTmp, 0, object.length);
        object = objectTmp;
        objectTmp = null;
} 

object[index] = new Exam(firstName, lastName, ID, examTypeCasted, score);

如果object数组已满，则策略是将其长度加倍。

如何从Scanner对象设置数组大小

2 个答案: