java - 程序错误不会打印部分代码

Question

你好，我的程序在 int pos = P.get(i); 方面给了我错误

它将编译并打印元素和元素的位置，但不会打印

pos val 代码的一部分，如果你能帮我找出代码的哪一部分是错误的并修复它

import java.util.*;

public class printlots {

//printlots procedure implementation

public static void printLots(List L, List P){


//display the table heading
System.out.println("pos\tval");
System.out.println("----------");

//repeat the loop for all positions in the list P
for(int i = 0; i < P.size();i++){

    //get current position from the list P
    int pos = P.get(i);
    //get the value (from the list L) stored at the current position
    int val = L.get(pos);
    //display the position and its corresponding value
    System.out.println(pos + "\t" + val);
}
}
//main method
public static void main(String[]args){
//create a list to store several elements
List L = new ArrayList();
//create several elements
List P = new ArrayList();
//add several elements to the list l

L.add(10);
L.add(20);
L.add(30);
L.add(40);
L.add(50);
L.add(60);
L.add(70);
L.add(80);
//add several positions to the list P

P.add(1);
P.add(3);
P.add(4);
P.add(6);

//print the values stored in the two list
System.out.println("Elements: " + L);
System.out.println("Positions: " + P);
System.out.println();
}


}

Answer 1

请不要使用raw-types 。并调用您的方法。

List<Integer> L = new ArrayList<>();
List<Integer> P = new ArrayList<>();
// ...
printLots(L, P);

并更改您的方法声明以采用参数化类型，例如

public static void printLots(List<Integer> L, List<Integer> P){