如何根据订单从ArrayList获取不常见的元素

Question

I am comparing two ArrayLists based on the Order

The size of total_list will be always bigger than the sub_list

import java.util.ArrayList;

import org.json.JSONException;

public class MrTest {

    public static void main(String args[]) throws JSONException
    {



        ArrayList<String> total_list = new ArrayList<String>();
        ArrayList<String> sub_list = new ArrayList<String>();

        ArrayList<String> un_common_list = new ArrayList<String>();

        total_list.add("Beverages");
        total_list.add("Hot");
        total_list.add("Sai1");
        total_list.add("Sai2");
        total_list.add("Sai3");


        sub_list.add("Sai1");
        sub_list.add("Sai2");
        sub_list.add("Sai3");




        for(int i=0;i<total_list.size();i++)
        {

            String total_name = total_list.get(i);
            String sub_name = sub_list.get(i);

            if(total_name.equals(sub_name))
            {

            }
            else
            {
                un_common_list.add(total_name);
            }


        }


        System.out.println(un_common_list);
    }
}

I am getting

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 3, Size: 3
    at java.util.ArrayList.rangeCheck(ArrayList.java:604)
    at java.util.ArrayList.get(ArrayList.java:382)
    at MrTest.main(MrTest.java:35)

where as i am expecting the output as

[Beverages, Hot]

Could anybody pleasse help me , as how to get Output as

[Beverages, Hot] in this case ??

Answer 1

I think you just want:

total_list.removeAll(sub_list);

If you want to preserve total_list :

List<String> uncommon = new ArrayList<>(total_list);
uncommon.removeAll(sub_list);

Answer 2

You are using the same index for both lists, causing the sublist to go out of bounds. Use a loop within a loop, and use a boolean to check if it matches any of the values, if it didnt match, then it should add the string to the uncommon list.

boolean inlist=false;
 for(int i=0;i<total_list.size();i++)
    {

        String total_name = total_list.get(i);

        for(int k=0;k<sub_list.size();k++)
        {
            String sub_name = sub_list.get(k);


            if(total_name.equals(sub_name))
            {
              inlist=true;
            }

        }
       if (!inlist){un_common_list.add(total_name);}
       inlist=false;
  }

Answer 3

    for(int i=0;i<total_list.size();i++) 
    // Total_list size is 5
    {

        String total_name = total_list.get(i);
        String sub_name = sub_list.get(i);
        // sub_list size is 3, 
        // but you are calling sublist.get(3), sublist.get(4) and sublist.get(5)
    }

Answer 4

i would go with 1 loop, first make a copy of total_list using System.arraycopy to un_common_list, then iterate the sub_list and remove elements present in sub_list from the un_common_list, order should be preserved

however the removeAll() should preserve order too, just use the array copy thing

Answer 5

如果要保持插入顺序，那么可以尝试这种情况

for(int i=0;i<total_list.size() && i<sub_list.size();i++)