Hyper-pedantic error/warning settings for Eclipse Oxygen (probably works on Neon too). Create a folder named ".settings" in the project folder and place this there

org.eclipse.jdt.core.prefs

eclipse.preferences.version=1
org.eclipse.jdt.core.compiler.annotation.inheritNullAnnotations=disabled
org.eclipse.jdt.core.compiler.annotation.missingNonNullByDefaultAnnotation=ignore
org.eclipse.jdt.core.compiler.annotation.nonnull=org.eclipse.jdt.annotation.NonNull
org.eclipse.jdt.core.compiler.annotation.nonnull.secondary=
org.eclipse.jdt.core.compiler.annotation.nonnullbydefault=org.eclipse.jdt.annotation.NonNullByDefault
org.eclipse.jdt.core.compiler.annotation.nonnullbydefault.secondary=
org.eclipse.jdt.core.compiler.annotation.nullable=org.eclipse.jdt.annotation.Nullable
org.eclipse.jdt.core.compiler.annotation.nullable.secondary=
org.eclipse.jdt.core.compiler.annotation.nullanalysis=disabled
org.eclipse.jdt.core.compiler.doc.comment.support=enabled
org.eclipse.jdt.core.compiler.problem.APILeak=warning
org.eclipse.jdt.core.compiler.problem.annotationSuperInterface=warning
org.eclipse.jdt.core.compiler.problem.autoboxing=ignore
org.eclipse.jdt.core.compiler.problem.comparingIdentical=warning
org.eclipse.jdt.core.compiler.problem.deadCode=warning
org.eclipse.jdt.core.compiler.problem.deprecation=warning
org.eclipse.jdt.core.compiler.problem.deprecationInDeprecatedCode=disabled
org.eclipse.jdt.core.compiler.problem.deprecationWhenOverridingDeprecatedMethod=disabled
org.eclipse.jdt.core.compiler.problem.discouragedReference=warning
org.eclipse.jdt.core.compiler.problem.emptyStatement=warning
org.eclipse.jdt.core.compiler.problem.explicitlyClosedAutoCloseable=warning
org.eclipse.jdt.core.compiler.problem.fallthroughCase=warning
org.eclipse.jdt.core.compiler.problem.fatalOptionalError=disabled
org.eclipse.jdt.core.compiler.problem.fieldHiding=info
org.eclipse.jdt.core.compiler.problem.finalParameterBound=warning
org.eclipse.jdt.core.compiler.problem.finallyBlockNotCompletingNormally=warning
org.eclipse.jdt.core.compiler.problem.forbiddenReference=warning
org.eclipse.jdt.core.compiler.problem.hiddenCatchBlock=warning
org.eclipse.jdt.core.compiler.problem.includeNullInfoFromAsserts=disabled
org.eclipse.jdt.core.compiler.problem.incompatibleNonInheritedInterfaceMethod=warning
org.eclipse.jdt.core.compiler.problem.incompleteEnumSwitch=warning
org.eclipse.jdt.core.compiler.problem.indirectStaticAccess=info
org.eclipse.jdt.core.compiler.problem.invalidJavadoc=warning
org.eclipse.jdt.core.compiler.problem.invalidJavadocTags=disabled
org.eclipse.jdt.core.compiler.problem.invalidJavadocTagsDeprecatedRef=disabled
org.eclipse.jdt.core.compiler.problem.invalidJavadocTagsNotVisibleRef=disabled
org.eclipse.jdt.core.compiler.problem.invalidJavadocTagsVisibility=public
org.eclipse.jdt.core.compiler.problem.localVariableHiding=ignore
org.eclipse.jdt.core.compiler.problem.methodWithConstructorName=warning
org.eclipse.jdt.core.compiler.problem.missingDefaultCase=ignore
org.eclipse.jdt.core.compiler.problem.missingDeprecatedAnnotation=ignore
org.eclipse.jdt.core.compiler.problem.missingEnumCaseDespiteDefault=disabled
org.eclipse.jdt.core.compiler.problem.missingHashCodeMethod=warning
org.eclipse.jdt.core.compiler.problem.missingJavadocComments=warning
org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsOverriding=disabled
org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsVisibility=public
org.eclipse.jdt.core.compiler.problem.missingJavadocTagDescription=return_tag
org.eclipse.jdt.core.compiler.problem.missingJavadocTags=info
org.eclipse.jdt.core.compiler.problem.missingJavadocTagsMethodTypeParameters=disabled
org.eclipse.jdt.core.compiler.problem.missingJavadocTagsOverriding=disabled
org.eclipse.jdt.core.compiler.problem.missingJavadocTagsVisibility=public
org.eclipse.jdt.core.compiler.problem.missingOverrideAnnotation=warning
org.eclipse.jdt.core.compiler.problem.missingOverrideAnnotationForInterfaceMethodImplementation=enabled
org.eclipse.jdt.core.compiler.problem.missingSerialVersion=warning
org.eclipse.jdt.core.compiler.problem.missingSynchronizedOnInheritedMethod=info
org.eclipse.jdt.core.compiler.problem.noEffectAssignment=warning
org.eclipse.jdt.core.compiler.problem.noImplicitStringConversion=warning
org.eclipse.jdt.core.compiler.problem.nonExternalizedStringLiteral=ignore
org.eclipse.jdt.core.compiler.problem.nonnullParameterAnnotationDropped=warning
org.eclipse.jdt.core.compiler.problem.nonnullTypeVariableFromLegacyInvocation=warning
org.eclipse.jdt.core.compiler.problem.nullAnnotationInferenceConflict=error
org.eclipse.jdt.core.compiler.problem.nullReference=error
org.eclipse.jdt.core.compiler.problem.nullSpecViolation=error
org.eclipse.jdt.core.compiler.problem.nullUncheckedConversion=warning
org.eclipse.jdt.core.compiler.problem.overridingPackageDefaultMethod=warning
org.eclipse.jdt.core.compiler.problem.parameterAssignment=ignore
org.eclipse.jdt.core.compiler.problem.pessimisticNullAnalysisForFreeTypeVariables=warning
org.eclipse.jdt.core.compiler.problem.possibleAccidentalBooleanAssignment=error
org.eclipse.jdt.core.compiler.problem.potentialNullReference=warning
org.eclipse.jdt.core.compiler.problem.potentiallyUnclosedCloseable=warning
org.eclipse.jdt.core.compiler.problem.rawTypeReference=warning
org.eclipse.jdt.core.compiler.problem.redundantNullAnnotation=warning
org.eclipse.jdt.core.compiler.problem.redundantNullCheck=warning
org.eclipse.jdt.core.compiler.problem.redundantSpecificationOfTypeArguments=ignore
org.eclipse.jdt.core.compiler.problem.redundantSuperinterface=info
org.eclipse.jdt.core.compiler.problem.reportMethodCanBePotentiallyStatic=ignore
org.eclipse.jdt.core.compiler.problem.reportMethodCanBeStatic=ignore
org.eclipse.jdt.core.compiler.problem.specialParameterHidingField=disabled
org.eclipse.jdt.core.compiler.problem.staticAccessReceiver=warning
org.eclipse.jdt.core.compiler.problem.suppressOptionalErrors=enabled
org.eclipse.jdt.core.compiler.problem.suppressWarnings=enabled
org.eclipse.jdt.core.compiler.problem.syntacticNullAnalysisForFields=disabled
org.eclipse.jdt.core.compiler.problem.syntheticAccessEmulation=ignore
org.eclipse.jdt.core.compiler.problem.terminalDeprecation=warning
org.eclipse.jdt.core.compiler.problem.typeParameterHiding=warning
org.eclipse.jdt.core.compiler.problem.unavoidableGenericTypeProblems=enabled
org.eclipse.jdt.core.compiler.problem.uncheckedTypeOperation=warning
org.eclipse.jdt.core.compiler.problem.unclosedCloseable=warning
org.eclipse.jdt.core.compiler.problem.undocumentedEmptyBlock=ignore
org.eclipse.jdt.core.compiler.problem.unhandledWarningToken=warning
org.eclipse.jdt.core.compiler.problem.unlikelyCollectionMethodArgumentType=warning
org.eclipse.jdt.core.compiler.problem.unlikelyCollectionMethodArgumentTypeStrict=disabled
org.eclipse.jdt.core.compiler.problem.unlikelyEqualsArgumentType=info
org.eclipse.jdt.core.compiler.problem.unnecessaryElse=ignore
org.eclipse.jdt.core.compiler.problem.unnecessaryTypeCheck=info
org.eclipse.jdt.core.compiler.problem.unqualifiedFieldAccess=ignore
org.eclipse.jdt.core.compiler.problem.unusedDeclaredThrownException=warning
org.eclipse.jdt.core.compiler.problem.unusedDeclaredThrownExceptionExemptExceptionAndThrowable=enabled
org.eclipse.jdt.core.compiler.problem.unusedDeclaredThrownExceptionIncludeDocCommentReference=disabled
org.eclipse.jdt.core.compiler.problem.unusedDeclaredThrownExceptionWhenOverriding=disabled
org.eclipse.jdt.core.compiler.problem.unusedExceptionParameter=ignore
org.eclipse.jdt.core.compiler.problem.unusedImport=warning
org.eclipse.jdt.core.compiler.problem.unusedLabel=warning
org.eclipse.jdt.core.compiler.problem.unusedLocal=warning
org.eclipse.jdt.core.compiler.problem.unusedObjectAllocation=warning
org.eclipse.jdt.core.compiler.problem.unusedParameter=warning
org.eclipse.jdt.core.compiler.problem.unusedParameterIncludeDocCommentReference=disabled
org.eclipse.jdt.core.compiler.problem.unusedParameterWhenImplementingAbstract=disabled
org.eclipse.jdt.core.compiler.problem.unusedParameterWhenOverridingConcrete=disabled
org.eclipse.jdt.core.compiler.problem.unusedPrivateMember=warning
org.eclipse.jdt.core.compiler.problem.unusedTypeParameter=warning
org.eclipse.jdt.core.compiler.problem.unusedWarningToken=warning
org.eclipse.jdt.core.compiler.problem.varargsArgumentNeedCast=warning