异常
前言. 开发时候遇到内部类的问题.
- 异常
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).
- 代码如下
// 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;
}
}
// 继承方法的形式进行运行.
// 特别注意 局部类 No enclosing instance of type XXX is accessible. Must qualify 异常.
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;
}
解决措施
- 方法1
将局部类设置为静态的. 类名前添加<static>关键字即可.
static class Sum implements Function2<Integer, Integer, Integer> {
public Integer call(Integer a, Integer b) {
return a + b;
}
}
- 方法2
通过类名.局部类名访问即可. 即如下的new ParentClassName().new GetLength().
JavaRDD<Integer> linesRDD = distFile.map(new ParentClassName().new GetLength());
- 方法3
不使用局部类即可. 作为非public类型类写在一个文件即可.
Reference
[1] JAVA在编写内部类时No enclosing instance of type XXX is accessible. Must qualify原因及解决.
[2] No enclosing instance of type 类名 is accessible. Must qualify the allocation with.