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Java FileOutputStream String Writing


I’ve been having issues with a Java File. It's designed to write line after line in a test file as a log. Unfortunately it overwrites the same line every time I call it.

If anyone can help I would be eternally grateful as this has been driving me up the wall!

Code Below.

public abstract class Log {

    protected static String DefaultLogFileLocation = "c:\\LOG.txt";

    public static void ToFile(String pInputString) {
        FileOutputStream pOUTPUT;
        PrintStream pPRINT;
        try
        {
            pOUTPUT = new FileOutputStream(DefaultLogFileLocation);
            pPRINT = new PrintStream(pOUTPUT);
            pPRINT.println (pInputString + "\n");
            pPRINT.close();
        }
        catch (Exception e)
        {
            System.err.println ("Error writing to file");
        }
    }
}

Solution

  • You forgot to pass constructor parameter to specify you need to append data to file.

    pOUTPUT = new FileOutputStream(DefaultLogFileLocation, true);
    

    Also, why you don't use some Java Logging Framework? E.g. java.util.logging or log4j

    Example of log4j configuration to write to file:

    <log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
      <appender name="console" class="org.apache.log4j.ConsoleAppender"> 
        <param name="Target" value="System.out"/> 
        <layout class="org.apache.log4j.PatternLayout"> 
          <param name="ConversionPattern" value="%-5p %c{1} - %m%n"/> 
        </layout> 
      </appender> 
    
      <appender name="FILE" class="org.apache.log4j.DailyRollingFileAppender">
        <param name="file" value="C:\\LOG.TXT" />
        <param name="datePattern" value="'.'yyyy-MM" />
        <param name="append" value="true" />
        <layout class="org.apache.log4j.PatternLayout">
          <param name="ConversionPattern" value="%d [%t] %-5p %C{6} (%F:%L) - %m%n"/> 
        </layout>
      </appender> 
      <root> 
        <priority value ="debug" /> 
        <appender-ref ref="FILE" /> 
        <appender-ref ref="console" /> 
      </root>