異常
前言. 開發時候遇到內部類的問題.
- 異常
No enclosing instance of type SparkProgrammingGuide is accessible. Must qualify the allocation with an enclosing instance of type SparkProgrammingGuide (e.g. x.new A() where x is an instance of SparkProgrammingGuide).
- 代碼如下
// 注意
static class GetLength implements Function<String, Integer> {
public Integer call(String s) {
return s.length();
}
}
class Sum implements Function2<Integer, Integer, Integer> {
public Integer call(Integer a, Integer b) {
return a + b;
}
}
// 繼承方法的形式進行運行.
// 特別注意 局部類 No enclosing instance of type XXX is accessible. Must qualify 異常.
static int getTotalLengthByExtendsFunction(JavaSparkContext context) {
int totalLength = 0;
if (null != context) {
JavaRDD<String> distFile = context.textFile("data/wordcount/spark-overview.txt");
JavaRDD<Integer> linesRDD = distFile.map(new GetLength());
totalLength = linesRDD.reduce(new Sum());
}
return totalLength;
}
解決措施
- 方法1
將局部類設置爲靜態的. 類名前添加<static>關鍵字即可.
static class Sum implements Function2<Integer, Integer, Integer> {
public Integer call(Integer a, Integer b) {
return a + b;
}
}
- 方法2
通過類名.局部類名訪問即可. 即如下的new ParentClassName().new GetLength().
JavaRDD<Integer> linesRDD = distFile.map(new ParentClassName().new GetLength());
- 方法3
不使用局部類即可. 作爲非public類型類寫在一個文件即可.
Reference
[1] JAVA在編寫內部類時No enclosing instance of type XXX is accessible. Must qualify原因及解決.
[2] No enclosing instance of type 類名 is accessible. Must qualify the allocation with.