System memory 259522560 must be at least 4.718592

我不是女神ヾ 2021-10-29 08:10 103阅读 0赞

**\[学习笔记\]**

/\*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  
  
word:o1abc  
word:45  
word:o1abc  
word:77  
word:o1abc  
word:o1abc\*/  
for (String word : wordsList) \{  
System.out.println("word:" + word);  
\}  
/\* http://spark.apache.org/docs/latest/  
Interface PairFunction<T,K,V>  
A function that returns key-value pairs (Tuple2<K, V>), and can be used to construct PairRDDs.  
scala.Tuple2<K,V> call(T t)  
\*/  
/\*  
flatMap once, line is o1abc 45(这句说明前面语句再次被执行)  
in tuple2 word: o1abc  
  
  
文章转载原文：[https://blog.csdn.net/qq\_44596980/article/details/93385009][https_blog.csdn.net_qq_44596980_article_details_93385009]

转载于:https://www.cnblogs.com/haima1949/p/11338429.html

[https_blog.csdn.net_qq_44596980_article_details_93385009]: https://blog.csdn.net/qq_44596980/article/details/93385009