在Eclipse中運行apache mahout FP增長時的java.lang.NullPointerException

Question

我是apache mahout的新手。我正在嘗試使用Apache Mahout的FP增長算法來從Java運行它。這裏是我的代碼使用，

FPGrowth<String> fp = new FPGrowth<String>(); 
FileLineIterable file = new FileLineIterable(new File(FPInputFileName)); 
int minSupport = 2; 
int maxHeapSize = 50; 
Writer writer = null; 
StringOutputConverter output = new StringOutputConverter(new SequenceFileOutputCollector<Text,TopKStringPatterns>(writer)); 
String pattern = " "; //currently understood as splitter 
try{ 
     fp.generateTopKFrequentPatterns(new StringRecordIterator(file,pattern), fp.generateFList(new StringRecordIterator(file, pattern), minSupport), minSupport, maxHeapSize, null, output, null); 
}catch(Exception err){ 
    err.printStackTrace(); 
} 

我面臨以下錯誤：

java.lang.NullPointerException 
at org.apache.mahout.fpm.pfpgrowth.fpgrowth.FPGrowth.growth(FPGrowth.java:331) 
at org.apache.mahout.fpm.pfpgrowth.fpgrowth.FPGrowth.fpGrowth(FPGrowth.java:211) 
at org.apache.mahout.fpm.pfpgrowth.fpgrowth.FPGrowth.generateTopKFrequentPatterns(FPGrowth.java:302) 
at org.apache.mahout.fpm.pfpgrowth.fpgrowth.FPGrowth.generateTopKFrequentPatterns(FPGrowth.java:174) 
at myProgram.main(myProgram.java:96) 

如何解讀？這是因爲作家設置爲空？請幫忙。

問候， psun

Answer 1

該錯誤是因爲我沒有（）正確地調用方法generateTopKFrequentPatterns。一旦我修改了通話，就沒有錯誤。