Java FileOutputStream String Writing

问题

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");
        }
    }
}

回答1:

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>

回答2:

I suggest using the FileOutputStream constructor that has an append parameter.

Generally, get familiar with the Javadocs, they can answer simple questions like that much more quickly than people here.

回答3:

Try using pOUTPUT = new FileOutputStream(DefaultLogFileLocation, true);. [Javadoc][1] here.

[1]: http://java.sun.com/j2se/1.4.2/docs/api/java/io/FileOutputStream.html#FileOutputStream(java.io.File, boolean)

来源：https://stackoverflow.com/questions/3095009/java-fileoutputstream-string-writing

标签

java

string

file-io

fileoutputstream