Skip to main content

​
Overview

CsvUtils is a utility class that provides helper methods for parsing CSV and tab-delimited data, as well as safe string-to-integer conversion. This class is commonly used in Mapper classes to parse input data fields. Package: circlenet.common Source: /workspace/source/src/main/java/circlenet/common/CsvUtils.java:3

​
Methods

​
split()

Splits a CSV line into an array of string fields. 
public static String[] split(String line)
​
line
String
required
The CSV line to split
Returns: String[] - Array of field values (empty strings for empty fields) Implementation: Uses String.split(",", -1) to preserve empty trailing fields.

​
Example Usage

public class AccessCountMapper extends Mapper<LongWritable, Text, Text, IntWritable> {
    @Override
    protected void map(LongWritable key, Text value, Context context) 
            throws IOException, InterruptedException {
        String[] f = CsvUtils.split(value.toString());
        if (f.length >= 3) {
            pageId.set(f[2].trim());
            context.write(pageId, ONE);
        }
    }
}
From TaskBSimple.java:29 - parsing activity log entries.

​
splitTab()

Splits a tab-delimited line into an array of string fields. 
public static String[] splitTab(String line)
​
line
String
required
The tab-delimited line to split
Returns: String[] - Array of field values (empty strings for empty fields) Implementation: Uses String.split("\\t", -1) to preserve empty trailing fields.

​
Example Usage

public class CountMapper extends Mapper<LongWritable, Text, Text, Text> {
    @Override
    protected void map(LongWritable key, Text value, Context context) 
            throws IOException, InterruptedException {
        String[] f = CsvUtils.splitTab(value.toString());
        if (f.length >= 2) {
            outKey.set(f[0].trim());
            outVal.set("C," + f[1].trim());
            context.write(outKey, outVal);
        }
    }
}
From TaskBSimple.java:72 - parsing intermediate MapReduce output (tab-separated key-value pairs).

​
toInt()

Safely converts a string to an integer with a fallback value on parse failure. 
public static int toInt(String value, int fallback)
​
value
String
required
The string value to parse
​
fallback
int
required
The default value to return if parsing fails
Returns: int - Parsed integer value, or fallback if parsing fails Error Handling: Catches all exceptions during parsing and returns the fallback value. Automatically trims whitespace before parsing.

​
Example Usage

public class JoinReducer extends Reducer<Text, Text, NullWritable, Text> {
    @Override
    protected void reduce(Text key, Iterable<Text> values, Context context) 
            throws IOException, InterruptedException {
        int count = 0;
        for (Text t : values) {
            String[] p = CsvUtils.split(t.toString());
            if (p.length >= 2 && "C".equals(p[0])) {
                count = CsvUtils.toInt(p[1], 0);
            }
        }
        // Use count...
    }
}
From TaskBSimple.java:95 - safely parsing count values during join operation.

​
Usage Patterns

​
Parsing CSV Input Data

String[] fields = CsvUtils.split(value.toString());
if (fields.length == 5) {
    String userId = fields[0];
    String name = fields[1];
    int age = CsvUtils.toInt(fields[2], 0);
    String email = fields[3];
    String hobby = fields[4];
}

​
Parsing MapReduce Intermediate Output

MapReduce jobs output tab-separated key-value pairs by default: 
String[] fields = CsvUtils.splitTab(value.toString());
if (fields.length >= 2) {
    String key = fields[0];
    String value = fields[1];
}

​
Combining Split and ToInt

String[] f = CsvUtils.split(line);
if (f.length >= 4) {
    int count = CsvUtils.toInt(f[0], 0);
    long keyRank = (count * 1000000L) + seq++;
    // Process ranking...
}
From TaskBSimple.java:119 - parsing and ranking top results.

​
Design Notes

  • Utility Class: Constructor is private; all methods are static
  • Preserve Empty Fields: Both split methods use -1 limit to preserve trailing empty fields
  • Null Safety: toInt() handles any exception (null, empty, invalid format) with fallback
  • Performance: Simple delegation to Java standard library methods for efficiency

Build docs developers (and LLMs) love

Get started for freeTalk to us