Question

java中使用ArrayList如何修改里面的内容？





Answer 1

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

public class test1 {

public static void main(String[] args) {

List list2 = new ArrayList();

list2.add(1);
list2.add(2);
list2.add(3);
list2.add(4);

list2.set(2, 7);

for(int i = 0 ; i < list2.size(); i++){
System.out.println(list2.get(i));

}
}

}

这样就行了

他的API是
set(int index, E element)
用指定元素替换列表中指定位置的元素（可选操作）。

Answer 2

////////////////that's mine

import java.util.*;

public class StudentSorter{

public static void main(String [] as){
Student a = new Student("a", 80);
Student b = new Student("b", 90);
Student c = new Student("c", 70);
List list = new ArrayList();
list.add(a);
list.add(b);
list.add(c);
System.out.println("未修改前:");
for(Student s: list){
System.out.println(s);
}
a.setMark(100);
list.set(0, a);
System.out.println("已修改后:");
for(Student s: list){
System.out.println(s);
}

}

}

class Student implements Comparable{

private String name;
private int mark;

public Student(){}

public Student(String n, int m) {
name = n;
mark = m;
}

public void setMark(int m){
mark = m;
}

public int getMark(){

return mark;
}

public int compareTo(Object o) {
if(o instanceof Student) {
Student s = (Student)o;
return s.getMark() - this.getMark();
} else {
return -1;
}

}

public String toString(){
return name + ": " + mark;
}

}

Answer 3

不是结了么？