Java - 使用自定义对象增强了 ArrayList 的 for 循环

Question

鉴于这个带有 ArrayList 的 StudentList 类采用具有三个字段的 Student 对象：Roll number、Name 和 Marks，如何编写增强的 For 循环而不是下面代码中编写的常规 For 循环方法？

学生.java

public class Student {
private int rollNumber;
private String name;
private int marks;

public Student(int roll, String name, int marks){
    this.rollNumber=roll;
    this.name=name;
    this.marks=marks;
}

public int getRollNumber(){
    return this.rollNumber;
}

public String getName() {
    return name;
}

public int getMarks() {
    return marks;
  }
}

这是带有 Main 方法的 SudentList 类

学生名单.java

import java.util.ArrayList;
import java.util.List;

public class StudentList {
public static void main(String[] args) {

Student a = new Student(1, "Mark", 80);
Student b = new Student(2, "Kevin", 85);
Student c = new Student(3, "Richard", 90);

List<Student> studentList = new ArrayList<>();
studentList.add(a);
studentList.add(b);
studentList.add(c);

for (int i = 0; i < studentList.size(); i++) {
  System.out.println("Roll number: " + 
  studentList.get(i).getRollNumber() +
                ", Name: " + studentList.get(i).getName() + ", Marks: " + 
  studentList.get(i).getMarks());
    }
  }
}

Answer 1

foreach为您提供直接对象而不是索引

for (Student st : studentList) {
       System.out.println("Roll number: " +  st.getRollNumber() + ", Name: " + st.getName() + ", Marks: " + st.getMarks());
    }

所以每当你看到list.get()用直接对象引用替换它时，你就完成了。