[memory] SoftReference for ResourceCompilationUnit.contents #1743

Ability to reduce memory during searches that find many files

#1743

org.eclipse.jdt.core/model/org/eclipse/jdt/internal/core/util/ResourceCompilationUnit.java

@@ -13,6 +13,8 @@
  *******************************************************************************/
 package org.eclipse.jdt.internal.core.util;
 
+import java.lang.ref.SoftReference;
+
 import org.eclipse.core.resources.IFile;
 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.jdt.core.compiler.CharOperation;
@@ -24,7 +26,7 @@
 public class ResourceCompilationUnit implements ICompilationUnit {
 
 	private final IFile file;
-	private char[] contents;
+	private volatile SoftReference<char[]> contentRef;
 	private final char[] fileName;
 	private final char[] mainTypeName;
 	private final char[] module;
@@ -46,15 +48,22 @@ public ResourceCompilationUnit(IFile file, char[] mod) {
 
 	@Override
 	public char[] getContents() {
-		if (this.contents != null)
-			return this.contents;   // answer the cached source
-
-		// otherwise retrieve it
+		SoftReference<char[]> cr = this.contentRef;
+		if (cr != null) {
+			char[] cachedContents = cr.get();
+			if (cachedContents != null) {
+				return cachedContents;
+			}
+		}
+		char[] contents;
 		try {
-			return (this.contents = Util.getResourceContentsAsCharArray(this.file));
+			contents = Util.getResourceContentsAsCharArray(this.file);
 		} catch (CoreException e) {
-			return CharOperation.NO_CHAR;
+			contents = CharOperation.NO_CHAR;
 		}
+		 // softly cache the result:
+		this.contentRef = new SoftReference<>(contents);
+		return contents;
 	}
 
 	@Override