java.lang.IllegalArgumentException: Comparison method violates its general contract! 报错

代码：

public static void wbsSort(List<SendMessageEntity> sendMessageEntityList){
        Collections.sort(sendMessageEntityList, (o1, o2) -> {
            String wbsCode1Temp = o1.getWbsCode();
            String wbsCode2Temp = o2.getWbsCode();
            String wbsCode1 = wbsCode1Temp.replaceAll("\\.","");
            String wbsCode2 = wbsCode2Temp.replaceAll("\\.","");

            int pointNum1 = 9-wbsCode1Temp.split("\\.").length;
            int pointNum2 = 9-wbsCode2Temp.split("\\.").length;

            String zero1 = "";
            String zero2 = "";
            for(int index=0;index<pointNum1;index++){
                zero1 += "0";
            }
            for(int index=0;index<pointNum2;index++){
                zero2 += "0";
            }
            wbsCode1 = wbsCode1+ zero1;
            wbsCode2 = wbsCode2 +zero2;
            // 转换为long类型
            long wbsCodeLong1 = Long.parseLong(wbsCode1);
            long wbsCodeLong2 = Long.parseLong(wbsCode2);
            if(wbsCodeLong1 > wbsCodeLong2){
                return 1;
            }else{
                return -1;
            }
        });
    }

　　解决办法：

你的比较方法有可能违反了比较合同，因为当 wbsCodeLong1 和 wbsCodeLong2 相等时，方法没有处理平等的情况。你应该在 if 语句之后添加处理相等情况的逻辑，如下：

return Long.compare(wbsCodeLong1, wbsCodeLong2);

里使用 Long.compare 方法来简化比较逻辑，并处理相等情况。这应当符合比较方法的合同，避免异常。

public static void wbsSort(List<SendMessageEntity> sendMessageEntityList){
    Collections.sort(sendMessageEntityList, (o1, o2) -> {
        String wbsCode1Temp = o1.getWbsCode();
        String wbsCode2Temp = o2.getWbsCode();
        String wbsCode1 = wbsCode1Temp.replaceAll("\\.","");
        String wbsCode2 = wbsCode2Temp.replaceAll("\\.","");

        int pointNum1 = 9 - wbsCode1Temp.split("\\.").length;
        int pointNum2 = 9 - wbsCode2Temp.split("\\.").length;

        String zero1 = String.format("%0" + pointNum1 + "d", 0);
        String zero2 = String.format("%0" + pointNum2 + "d", 0);

        wbsCode1 = wbsCode1 + zero1;
        wbsCode2 = wbsCode2 + zero2;

        long wbsCodeLong1 = Long.parseLong(wbsCode1);
        long wbsCodeLong2 = Long.parseLong(wbsCode2);

        return Long.compare(wbsCodeLong1, wbsCodeLong2);
    });
}