System memory 259522560 must be at least 4.718592

/*没有下面的话， 会报一个错误，java.lang.IllegalArgumentException: System memory 259522560 must be at least 4.718592E8（470M）. Please use a larger heap size.这是memory不够，导致无法启动SparkContext*/        

        conf.set("spark.testing.memory", "2000000000");

        JavaSparkContext sc = new JavaSparkContext(conf);

/*下面的这种倒入的方法也行*/        

 //       JavaRDD<String> text = sc.textFile("hdfs://localhost:9000/README.txt");

/*原文件是：o1abc 45

o1abc 77

o1abc o1abc */        

        JavaRDD<String> text = sc.textFile("E://temp//input//friend.txt");

        List<String> strList = text.collect();

/*输出str:o1abc 45

str:o1abc 77

str:o1abc o1abc*/        

        for (String str : strList) {

            System.out.println("str:" + str);

        }

/*Interface FlatMapFunction<T,R>, Iterable<R> call(T t)(注意之后的版本，返回值有所变化。)*/        

        JavaRDD<String> words = text.flatMap(new FlatMapFunction<String, String>() {

/*List的super Interface 是java.lang.Iterable*/            

            public Iterable<String> call(String line) throws Exception {

                System.out.println("flatMap once, line is "+line );

                String[] wordsArray=line.split(" ");

                List<String> wordsList=Arrays.asList(wordsArray);

                return wordsList;

            }

        });

        List<String> wordsList = words.collect();

/*输出

flatMap once, line is o1abc 45

flatMap once, line is o1abc 77

flatMap once, line is o1abc o1abc

更多请见：https://blog.csdn.net/qq_44596980/article/details/93385009