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https://issues.apache.org/jira/browse/MNG-7899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17777986#comment-17777986
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ASF GitHub Bot commented on MNG-7899:
-------------------------------------
sebastien-doyon commented on code in PR #1296:
URL: https://github.com/apache/maven/pull/1296#discussion_r1367520121
##########
maven-embedder/src/main/java/org/apache/maven/cli/transfer/FileSizeFormat.java:
##########
@@ -0,0 +1,160 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.maven.cli.transfer;
+
+import java.text.DecimalFormat;
+import java.text.DecimalFormatSymbols;
+import java.util.Locale;
+
+/**
+ * Formats file size with the associated <a
href="https://en.wikipedia.org/wiki/Metric_prefix";>SI</a> prefix
+ * (GB, MB, kB) and using the patterns <code>#0.0</code> for numbers between 1
and 10
+ * and <code>###0</code> for numbers between 10 and 1000+ by default.
+ *
+ * @see <a
href="https://en.wikipedia.org/wiki/Metric_prefix";>https://en.wikipedia.org/wiki/Metric_prefix</a>
+ * @see <a
href="https://en.wikipedia.org/wiki/Binary_prefix";>https://en.wikipedia.org/wiki/Binary_prefix</a>
+ * @see <a
+ *
href="https://en.wikipedia.org/wiki/Octet_%28computing%29";>https://en.wikipedia.org/wiki/Octet_(computing)</a>
+ */
+public class FileSizeFormat {
+ enum ScaleUnit {
+ BYTE {
+ @Override
+ public long bytes() {
+ return 1L;
+ }
+
+ @Override
+ public String symbol() {
+ return "B";
+ }
+ },
+ KILOBYTE {
+ @Override
+ public long bytes() {
+ return 1000L;
+ }
+
+ @Override
+ public String symbol() {
+ return "kB";
+ }
+ },
+ MEGABYTE {
+ @Override
+ public long bytes() {
+ return KILOBYTE.bytes() * KILOBYTE.bytes();
+ }
+
+ @Override
+ public String symbol() {
+ return "MB";
+ }
+ },
+ GIGABYTE {
+ @Override
+ public long bytes() {
+ return MEGABYTE.bytes() * KILOBYTE.bytes();
+ }
+ ;
+
+ @Override
+ public String symbol() {
+ return "GB";
+ }
+ };
+
+ public abstract long bytes();
+
+ public abstract String symbol();
+
+ public static ScaleUnit getScaleUnit(long size) {
+ if (size < 0L) {
+ throw new IllegalArgumentException("file size cannot be
negative: " + size);
+ }
+
+ if (size >= GIGABYTE.bytes()) {
+ return GIGABYTE;
+ } else if (size >= MEGABYTE.bytes()) {
+ return MEGABYTE;
+ } else if (size >= KILOBYTE.bytes()) {
+ return KILOBYTE;
+ } else {
+ return BYTE;
+ }
+ }
+ }
+
+ private DecimalFormat smallFormat;
+ private DecimalFormat largeFormat;
+
+ public FileSizeFormat(Locale locale) {
+ smallFormat = new DecimalFormat("#0.0", new
DecimalFormatSymbols(locale));
+ largeFormat = new DecimalFormat("###0", new
DecimalFormatSymbols(locale));
+ }
+
+ public String format(long size) {
+ return format(size, ScaleUnit.getScaleUnit(size));
+ }
+
+ public String getScaleSymbol(long size) {
+ return ScaleUnit.getScaleUnit(size).symbol();
+ }
+
+ @SuppressWarnings("checkstyle:magicnumber")
+ private String format(long size, ScaleUnit unit) {
+ if (size < 0L) {
+ throw new IllegalArgumentException("file size cannot be negative:
" + size);
+ }
+
+ double scaledSize = (double) size / unit.bytes();
+
+ if (unit == ScaleUnit.BYTE) {
+ return largeFormat.format(size);
Review Comment:
Using a Formatter, the pattern string is passed as parameter to the format()
method. Doing this the pattern is recompiled each method call and not reused.
This generates a lot of garbage. A more optimised solution would be to avoid
using generic Format or Formatter classes and implement a custom logic specific
to this particular case. Some math logic to round the numbers as needed. This
would reduce even more the memory allocation.
> Various memory usage improvements
> ---------------------------------
>
> Key: MNG-7899
> URL: https://issues.apache.org/jira/browse/MNG-7899
> Project: Maven
> Issue Type: Improvement
> Components: Design, Patterns & Best Practices, Embedding,
> General, Logging
> Affects Versions: 4.0.0-alpha-2
> Reporter: sebastien
> Priority: Major
>
> Some optimisations can be applied to the code to reduce the use of temporary
> objects.
> Typical improvements identified are:
> * reduce scope of temporary objects creation to avoid creating when not
> needed. Example :
> {code:java}
> public String toString() {
> StringBuilder sb = new StringBuilder(512);
> if (isEmpty()) {
> return "empty";
> }
> for (MetadataGraphVertex v : vertices) {
> .....{code}
> can be replaced by
> {code:java}
> public String toString() {
> if (isEmpty()) {
> return "empty";
> }
> StringBuilder sb = new StringBuilder(512);
> for (MetadataGraphVertex v : vertices) {
> .....{code}
> * Reuse StringBuilder objects in loops by setting its length to zero
> * Use the StringBuilder.append() with index to avoid String.substring().
> Example:
>
> {code:java}
> int idx = resourceName.lastIndexOf('/');
> buffer.append(idx < 0 ? resourceName : resourceName.substring(idx + 1));
> {code}
> can be replaced by
>
> {code:java}
> int idx = resourceName.lastIndexOf('/');
> if (idx < 0) {
> buffer.append(resourceName);
> } else {
> buffer.append(resourceName, idx + 1, resourceName.length());
> } {code}
>
>
> * Replace dynamic string creation static constants when possible
> * Avoid creating temporary strings with + operator when the final
> destination can be used instead, like PrintStream.print() method
> * Avoir using StringBuilder.append() method and util method MessageUtils.a()
> when the final destination can be used instead, like PrintStream.print()
> method
>
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