全球简讯:Cannot Reference “XxxClass.xxx” Before Supertype Constructor Has Been Called

• 2023-06-15 13:16:32 来源：博客园

【资料图】

百度翻译：在调用超类型构造函数之前无法引用“XxxClass.xxx” ----- 我的理解：一个类的构造器方法还未执行的时候，我们无法使用类的成员属性或成员方法。

下面是此错误的示例代码

public class MyException extends RuntimeException {    private int errorCode = 0;        public MyException(String message) {        super(message + getErrorCode()); // compilation error    }    public int getErrorCode() {        return errorCode;    }}

IDE提示错误：

说说我怎么遇到这个问题的？

我有一个组件工具类。

1 @Slf4j 2 public class Many2OneProcessor { 3  4     private static ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(15); 5  6     /** 7      * 将多长时间的多次操作合并成1次，单位：秒 8      */ 9     private final long intervalSecond;10     /**11      * 每次处理多少条数据12      */13     private final int perBatchCount;14     /**15      * 批次处理逻辑代码16      */17     private final Consumer> yourBusinessCode;18     private final ...19 20     public Many2OneProcessor(long intervalSecond, Class tClass, Consumer> yourBusinessCode) {21         this(intervalSecond, Integer.MAX_VALUE, tClass, yourBusinessCode);22     }23 24     public Many2OneProcessor(long intervalSecond, int perBatchCount, Class tClass, Consumer> yourBusinessCode) {25         26         ...此处省略若干行27         28     }    29     30     public void produce(T t) {31         redisUtil.lSet(LIST_KEY, t, HOURS.toMillis(1));32         scheduledThreadPool.schedule(this::consumeMsg, intervalSecond, TimeUnit.SECONDS);33     }34 35     public void consumeMsg() {36         redisLockTemplate.execute(LOCK_KEY, TimeUnit.SECONDS.toMillis(intervalSecond - 1), false, () -> {37             38             ...39             40             List tList = new ArrayList<>(perBatchCount + 1);41             for (int j = 0; j < perBatchCount; j++) {42                 Object o = redisUtil.lPop(LIST_KEY);43                 if (o == null) break;44                 tList.add((T) o);45             }46             if (perBatchCount != Integer.MAX_VALUE && redisUtil.lGetListSize(LIST_KEY) > 0) {47                 scheduledThreadPool.schedule(this::consumeMsg, intervalSecond, TimeUnit.SECONDS);48             }49             50             ...51             yourBusinessCode.accept(tList);52             53         });54     }55 }

注意到其中的两处Integer.MAX_VALUE。这无形中提高了代码理解和维护（重点是前者）的成本。

于是，做点重构。改为下面这样，代码的可理解方面，更上一层楼。

public class Many2OneProcessor {    /**     * 每次处理多少条数据     */    private final int perBatchCount;    private static final int PER_BATCH_COUNT_DEFAULT = Integer.MAX_VALUE;        public Many2OneProcessor(long intervalSecond, Class tClass, Consumer> yourBusinessCode) {        this(intervalSecond, PER_BATCH_COUNT_DEFAULT, tClass, yourBusinessCode);    }        public void consumeMsg() {        ...                    if (perBatchCount != PER_BATCH_COUNT_DEFAULT && redisUtil.lGetListSize(LIST_KEY) > 0) {        ...    }}

注意，PER_BATCH_COUNT_DEFAULT 需要定义为static。否则会出现上面的预编译错误。Cannot reference "Many2OneProcessor.PER_BATCH_COUNT_DEFAULT" before supertype constructor has been called。另外，在重构过程中，我使用了一种方案，见下图，也出现了这个错误：Cannot reference "Many2OneProcessor.perBatchCount" before supertype constructor has been called

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