Bug 562122 - Improve performance of ClasspathJar.hasCompilationUnitI20200424-1800

Check the existing "knownPackageNames" cache first and return early when
possible without walking over zip file entries.

Change-Id: Iea26725ae8864d2cc74478bf3a152a9b53dd3138
Signed-off-by: alee <andy.ja.lee@gmail.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/org.eclipse.jdt.core/model/org/eclipse/jdt/internal/core/builder/ClasspathJar.java b/org.eclipse.jdt.core/model/org/eclipse/jdt/internal/core/builder/ClasspathJar.java
index 365a8ab77f..ba153dfef3 100644
--- a/org.eclipse.jdt.core/model/org/eclipse/jdt/internal/core/builder/ClasspathJar.java
+++ b/org.eclipse.jdt.core/model/org/eclipse/jdt/internal/core/builder/ClasspathJar.java
@@ -326,6 +326,15 @@ public boolean isPackage(String qualifiedPackageName, String moduleName) {
 @Override
 public boolean hasCompilationUnit(String pkgName, String moduleName) {
 	if (scanContent()) {
+		if (!this.knownPackageNames.includes(pkgName)) {
+			// Don't waste time walking through the zip if we know that it doesn't
+			// contain a directory that matches pkgName
+			return false;
+		}
+
+		// Even if knownPackageNames contained the pkg we're looking for, we still need to verify
+		// that the package in this jar actually contains at least one .class file (since
+		// knownPackageNames includes empty packages)
 		for (Enumeration<? extends ZipEntry> e = this.zipFile.entries(); e.hasMoreElements(); ) {
 			String fileName = e.nextElement().getName();
 			if (fileName.startsWith(pkgName)
@@ -334,6 +343,7 @@ public boolean hasCompilationUnit(String pkgName, String moduleName) {
 				return true;
 		}
 	}
+
 	return false;
 }