java - 无法让字符串compareTo方法工作

Question

由于某种原因，我无法让 StringscompareTo 方法工作。我收到此错误消息:

exception in thread main java.lang.NullpointerException
at java.lang.String.compareTo(Unknown Source)
at Sort.main(Sort.java:27)

我可以做什么来解决这个问题？ (此代码要求 to 数组都已单独排序。)

import java.util.*;

class Sort{
    public static void main(String[] args){
        String[] ord = new String[6];
        ord[0] = "astra";
        ord[1] = "bilum";
        ord[2] = "deliber";
        ord[3] = "kaliber";
        ord[4] = "suppe";
        ord[5] = "vorte";

        String[] ordet = new String[6];
        ord[0] = "akilles";
        ord[1] = "kopper";
        ord[2] = "lipton";
        ord[3] = "mus";
        ord[4] = "orkester";
        ord[5] = "toving";

        String[] flettet = new String[ord.length + ordet.length];

        for(int i = 0; i < ord.length; i++){
            int teller = i; 
            for(int j = 0; j < ordet.length; j++){
                if(ord[i].compareTo(ordet[j]) > 0){ //line 27
                    teller += 1;
                }
            }
            flettet[teller] = ord[i];
        }
    }   
}

Answer 1

您的意思是 - 看起来您设置了错误的数组:

    String[] ordet = new String[6];
    ordet[0] = "akilles";
    ordet[1] = "kopper";
    ordet[2] = "lipton";
    ordet[3] = "mus";
    ordet[4] = "orkester";
    ordet[5] = "toving";