### Eclipse Workspace Patch 1.0
#P org.eclipse.jdt.core
Index: compiler/org/eclipse/jdt/internal/compiler/flow/LoopingFlowContext.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/flow/LoopingFlowContext.java,v
retrieving revision 1.51
diff -u -r1.51 LoopingFlowContext.java
--- compiler/org/eclipse/jdt/internal/compiler/flow/LoopingFlowContext.java	23 Aug 2010 08:41:25 -0000	1.51
+++ compiler/org/eclipse/jdt/internal/compiler/flow/LoopingFlowContext.java	9 Feb 2011 17:26:22 -0000
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2010 IBM Corporation and others.
+ * Copyright (c) 2000, 2011 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -519,7 +519,7 @@
 						flowInfo.initsWhenTrue().setReachMode(FlowInfo.UNREACHABLE);
 					}
 				}
-			} else if (this.upstreamNullFlowInfo.isDefinitelyNonNull(local) && !flowInfo.isPotentiallyNull(local)) {    // https://bugs.eclipse.org/bugs/show_bug.cgi?id=291418
+			} else if (this.upstreamNullFlowInfo.isDefinitelyNonNull(local) && !flowInfo.isPotentiallyNull(local) && !flowInfo.isPotentiallyUnknown(local)) {    // https://bugs.eclipse.org/bugs/show_bug.cgi?id=291418
 				flowInfo.markAsDefinitelyNonNull(local);
 				if ((this.tagBits & FlowContext.HIDE_NULL_COMPARISON_WARNING) == 0) {
 					recordNullReference(local, reference, checkType);
#P org.eclipse.jdt.core.tests.compiler
Index: src/org/eclipse/jdt/core/tests/compiler/regression/NullReferenceTest.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/NullReferenceTest.java,v
retrieving revision 1.111
diff -u -r1.111 NullReferenceTest.java
--- src/org/eclipse/jdt/core/tests/compiler/regression/NullReferenceTest.java	8 Feb 2011 05:59:20 -0000	1.111
+++ src/org/eclipse/jdt/core/tests/compiler/regression/NullReferenceTest.java	9 Feb 2011 17:26:29 -0000
@@ -13947,4 +13947,82 @@
 		},
 		"SUCCESS");
 }
+
+// https://bugs.eclipse.org/bugs/show_bug.cgi?id=313870
+public void testBug313870() {
+	this.runConformTest(
+		new String[] {
+			"X.java",
+			"public class X {\n" + 
+			"	public static void main(String[] args) {\n" +
+			"		String s = \"\";\n" +
+			"		for (int i = 0; i < 2; i++) {\n" +
+            "			if (i != 0) { \n" +
+            "    			s = test();\n" +
+            "			}\n" +
+            "			if (s == null) {\n" +
+            "    			System.out.println(\"null\");\n" +
+            "			}\n" +
+            "		}\n" + 
+			"	}\n" + 
+			"	public static String test() {\n" +
+            "		return null;\n" +
+			"	}\n" + 
+			"}"
+		},
+		"null");
+}
+
+// https://bugs.eclipse.org/bugs/show_bug.cgi?id=313870
+public void testBug313870b() {
+	this.runConformTest(
+		new String[] {
+			"X.java",
+			"import java.io.BufferedReader;\n" +
+			"import java.io.IOException;\n" +
+			"public class X {\n" + 
+			"	public void main(BufferedReader bufReader) throws IOException {\n" +
+			"		String line = \"\";\n" +
+			"		boolean doRead = false;\n" +
+			"		while (true) {\n" +
+            "			if (doRead) { \n" +
+            "    		   line = bufReader.readLine();\n" +
+            "			}\n" +
+            "			if (line == null) {\n" +
+            "    			return;\n" +
+            "			}\n" +
+            "			doRead = true;\n" +
+            "		}\n" +
+			"	}\n" + 
+			"}"
+		},
+		"");
+}
+
+// https://bugs.eclipse.org/bugs/show_bug.cgi?id=313870
+public void testBug313870c() {
+	this.runConformTest(
+		new String[] {
+			"X.java",
+			"import java.io.File;\n" +
+			"public class X {\n" + 
+			"	public static void main(String[] args) {\n" +
+			"		boolean sometimes = (System.currentTimeMillis() & 1L) != 0L;\n" +
+			"		File file = new File(\"myfile\");\n" +
+			"		for (int i = 0; i < 2; i++) {\n" +
+            "			if (sometimes) { \n" +
+            "    		 	file = getNewFile();\n" +
+            "			}\n" +
+            "			if (file == null) { \n" +
+            "    			System.out.println(\"\");\n" +
+            "			}\n" +
+            "		}\n" +
+			"	}\n" +
+			"	private static File getNewFile() {\n" +
+			"		return null;\n" +
+			"	}\n" + 
+			"}"
+		},
+		"");
+}
 }
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