Bug 50574 quick fix for removing local variable that is never read changes side effects
You'll need to set the "Local variable is never read" option in Window>Preferences>Java>Compiler>Unused Code to something other than "Ignore" to reproduce this. The quick fix "Remove variable <variable name> and assignments without possible side effects" that is offered if a local variable is never read makes two types of mistakes: 1. Some side effects are not recognized, e.g. "fixing" int k = 3; int n; n = k++; System.out.println (k); yields int k = 3; System.out.println (k); 2. The variable definition is removed even if it has side effects, e.g. int n = System.in.read (); is removed, whereas if a later assignment has side effects, it is left unchanged, including the now undefined reference to the local variable, e.g. int n; n = System.in.read (); becomes n = System.in.read (); What I think *should* happen is that the initializing assignment and later assignments should be treated alike; the left-hand side referring to the local variable should *always* be removed, and the right-hand side should be removed if and only if it has no side effects. This may result in invalid code if the right-hand side expression has side effects but does not form a statement; a deluxe version might extract the parts that have side effects and insert them as statements in the correct order, but even without this there would be a significant improvement over the current behaviour, which changes side effects and leaves references to undefined variables around.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/text/correction/RemoveDeclarationCorrectionProposal.java
SimpleName[] references= LinkedNodeFinder.findByBinding(completeRoot, nameNode.resolveBinding());
			for (int i= 0; i < references.length; i++) {
				removeVariableReferences(rewrite, references[i]);
			}
			
			ASTNode declaringNode= completeRoot.findDeclaringNode(nameNode.resolveBinding());
			if (declaringNode instanceof SingleVariableDeclaration) {
				if (declaringNode.getParent() instanceof MethodDeclaration) {
					Javadoc javadoc= ((MethodDeclaration) declaringNode.getParent()).getJavadoc();
					if (javadoc != null) {
						TagElement tagElement= findThrowsTag(javadoc, nameNode.resolveBinding());
						if (tagElement != null) {
							rewrite.markAsRemoved(tagElement);
						}
					}
				}
			}
		}
		return rewrite;
	}
	
	private static TagElement findThrowsTag(Javadoc javadoc, IBinding binding) {
		List tags= javadoc.tags();
		for (int i= tags.size() - 1; i >= 0; i--) {
			TagElement curr= (TagElement) tags.get(i);
			String currName= curr.getTagName();
			if ("@param".equals(currName)) {  
				List fragments= curr.fragments();
				if (!fragments.isEmpty() && fragments.get(0) instanceof Name) {
					Name name= (Name) fragments.get(0);