Array Java programming: source code sample for simple Java arrays.

How to read lines of a text file into a very simple fixed size array. Also shows how to sort the array content alphabetically, and how to write array content as another text file.

/*
 Java array source code example:
 - read text file into a simple array
 - with fixed maximum number of lines
 - sort the array
 - write array content into another text file.
 Put this text into a file tmp1.java.
*/
import java.io.*;
public class tmp1
{
 // how many text lines can this program read?
 int MAX_TEXT_LINES = 1000; // up to 1000 lines
 // static start point (no object yet)
 public static void main(String args[]) throws Throwable
 { new tmp1().main2(args); }
 // dynamic start point (on a single object)
 public int main2(String args[]) throws Throwable
 {
 if (args.length < 2)
 return 9+perr("supply in- and output filename.");
 String sInFile = args[0];
 String sOutFile = args[1];
 // very simple static array for text storage:
 String aTextData[] = new String[MAX_TEXT_LINES+10];
 // +10 are safety spaces, to avoid crash on off-by-one errors.
 int iTextSize = MAX_TEXT_LINES; // how large is the array
 int iTextUsed = 0; // how many lines contained
 // read input file into the array.
 BufferedReader fin = new BufferedReader(
 new InputStreamReader(
 new FileInputStream(args[0]), "ISO-8859-1"
 // or US-ASCII,UTF-8,UTF-16BE,UTF-16LE,UTF-16
 ));
 while (true)
 {
 String sLine = fin.readLine();
 if (sLine == null)
 break; // end of file
 // check if array has space for another line
 if (iTextUsed >= iTextSize)
 { perr("overflow: too many text lines\n"); break; }
 aTextData[iTextUsed] = sLine;
 iTextUsed++;
 }
 fin.close();
 // do some processing on the array contents
 processData(aTextData, iTextUsed, iTextSize);
 // write the whole array to output file.
 PrintWriter fout = new PrintWriter(
 new OutputStreamWriter(
 new FileOutputStream(args[1]), "ISO-8859-1"
 ));
 for (int iLine=0; iLine<iTextUsed; iLine++)
 {
 fout.println(aTextData[iLine]);
 }
 fout.close();
 return 0;
 }
 // processing example: sort array text lines alphabetically
 // with the simplest possible sorting algorithm (bubblesort).
 int processData(String aText[], int iLinesUsed, int iLinesAlloced)
 {
 int iOuterIdx, iInnerIdx;
 for (iOuterIdx=0; iOuterIdx<iLinesUsed; iOuterIdx++)
 {
 for (iInnerIdx=iOuterIdx+1; iInnerIdx<iLinesUsed; iInnerIdx++)
 {
 String sLine1 = aText[iOuterIdx];
 String sLine2 = aText[iInnerIdx];
 if (sLine1.compareTo(sLine2) > 0)
 {
 // swap both lines
 aText[iOuterIdx] = sLine2;
 aText[iInnerIdx] = sLine1;
 }
 }
 }
 print("sorted "+iLinesUsed+" lines.\n");
 return 0;
 }
 // alternative processing example: sort using the Arrays class
 int processData2(String aText[], int iLinesUsed, int iLinesAlloced)
 {
 java.util.Arrays.sort(aText, 0, iLinesUsed);
 return 0;
 }
 // helper functions for better readability
 static int perr(String s)
 { System.err.print("error: "+s); return 0; }
 static int print(String s)
 { System.out.print(s); return 0; }
};

// See also: Java example for variable sized array .

imprint / impressum