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  1. JDK
  2. JDK-7129417

Compress Strings dropped in Java 7, listed as on by default in docs.

    Details

    • Type: Bug
    • Status: Resolved
    • Priority: P4
    • Resolution: Won't Fix
    • Affects Version/s: 8
    • Fix Version/s: 8
    • Component/s: docs
    • Subcomponent:
    • CPU:
      x86
    • OS:
      linux

      Description

      FULL PRODUCT VERSION :


      A DESCRIPTION OF THE PROBLEM :
      On this page it lists -XX:+UseCompressedStrings as on by default.

      http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html

       However in Java 6 update 29 its off by default and in Java 7 update 2 it reports

      Java HotSpot(TM) 64-Bit Server VM warning: ignoring option UseCompressedStrings; support was removed in 7.0

      The program below requires a heap of 2000m on Java 7, 1800m on Java 6 without compressed Strings and 1000m with compressed Strings. Its also faster with compressed Strings turned on.

      REGRESSION. Last worked in version 7

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Try Java 6 and 7 with and without UseCompressedStrings

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      Options to improve performance to retained

      OR

      The documentation to reflect which options are available. A note as to why its not available would be very interesting.
      ACTUAL -
      Neither

      ERROR MESSAGES/STACK TRACES THAT OCCUR :
      OutOfMemoryError if you don't have 2 GB for the heap.

      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------
      import java.io.*;
      import java.util.ArrayList;
      import java.util.Collections;
      import java.util.List;

      public class Main {
          public static void main(String... args) throws IOException {
              long start = System.nanoTime();
              generateFile("lines.txt", 755 * 1024 * 1024, 189000);

              List<String> lines = loadLines("lines.txt");

              System.out.println("Sorting file");
              Collections.sort(lines);
              System.out.println("... Sorted file");
              // save lines.
              long time = System.nanoTime() - start;
              System.out.printf("Took %.3f second to read, sort and write to a file%n", time / 1e9);
          }

          private static void generateFile(String fileName, int size, int lines) throws FileNotFoundException {
              System.out.println("Creating file to load");
              int lineSize = size / lines;
              StringBuilder sb = new StringBuilder();
              while (sb.length() < lineSize) sb.append('-');
              String padding = sb.toString();

              PrintWriter pw = new PrintWriter(fileName);
              for (int i = 0; i < lines; i++) {
                  String text = (i + padding).substring(0, lineSize);
                  pw.println(text);
              }
              pw.close();
              System.out.println("... Created file to load");
          }

          private static List<String> loadLines(String fileName) throws IOException {
              System.out.println("Reading file");
              BufferedReader br = new BufferedReader(new FileReader(fileName));
              List<String> ret = new ArrayList<String>();
              String line;
              while ((line = br.readLine()) != null)
                  ret.add(line);
              System.out.println("... Read file.");
              return ret;
          }
      }

      ---------- END SOURCE ----------

      CUSTOMER SUBMITTED WORKAROUND :
      Use older version of Java until fixed.

      SUPPORT :
      YES

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            • Assignee:
              Unassigned
              Reporter:
              webbuggrp Webbug Group
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