Fix more spotbugs errors

ballerina-shell/modules/shell-cli/src/main/java/io/ballerina/shell/cli/jline/validator/ExpressionValidator.java

@@ -47,6 +47,6 @@ public boolean evaluate(String source) {
         IncompleteInputFinder incompleteInputFinder = new IncompleteInputFinder();
         Node parsedNode = NodeParser.parseExpression(source);
         return !parsedNode.hasDiagnostics() || !parsedNode.apply(incompleteInputFinder)
-                || nextInValidator.evaluate(source);
+                || (nextInValidator != null && nextInValidator.evaluate(source));
     }
 }

ballerina-shell/modules/shell-cli/src/main/java/io/ballerina/shell/cli/jline/validator/ModuleMemberValidator.java

@@ -61,11 +61,11 @@ public boolean evaluate(String source) {
             // Sample testcase : if (x == y) { x = x + 1; x = x + 1;
             if (lastNode.kind() == SyntaxKind.FUNCTION_DEFINITION) {
                 return !lastNode.hasDiagnostics() || !lastNode.apply(incompleteInputFinder)
-                        || nextInValidator.evaluate(lastNode.toSourceCode());
+                        || (nextInValidator != null && nextInValidator.evaluate(lastNode.toSourceCode()));
             }
         }
 
         return !node.imports().isEmpty() || !parsedNode.hasDiagnostics() || !parsedNode.apply(incompleteInputFinder)
-                || nextInValidator.evaluate(source);
+                || (nextInValidator != null && nextInValidator.evaluate(source));
     }
 }

ballerina-shell/modules/shell-cli/src/main/java/io/ballerina/shell/cli/jline/validator/StatementValidator.java

@@ -47,6 +47,6 @@ public boolean evaluate(String source) {
         IncompleteInputFinder incompleteInputFinder = new IncompleteInputFinder();
         Node parsedNode = NodeParser.parseBlockStatement("{" + source + "}");
         return !parsedNode.hasDiagnostics() || !parsedNode.apply(incompleteInputFinder)
-                || nextInValidator.evaluate(source);
+                || (nextInValidator != null && nextInValidator.evaluate(source));
     }
 }

bvm/ballerina-runtime/src/main/java/io/ballerina/runtime/internal/scheduling/AsyncUtils.java

@@ -131,7 +131,8 @@ public void notifyFailure(BError error) {
      * @param returnValueSupplier  Suppler used to set the final return value for the parent function invocation.
      * @param scheduler            The scheduler for invoking functions
      */
-    public static void invokeFunctionPointerAsyncIteratively(BFunctionPointer<Object[], ?> func, @Nullable String strandName,
+    public static void invokeFunctionPointerAsyncIteratively(BFunctionPointer<Object[], ?> func,
+                                                             @Nullable String strandName,
                                                              StrandMetadata metadata, int noOfIterations,
                                                              Supplier<Object[]> argsSupplier,
                                                              Consumer<Object> futureResultConsumer,

bvm/ballerina-runtime/src/main/java/io/ballerina/runtime/internal/scheduling/Scheduler.java

@@ -228,8 +228,8 @@ public FutureValue schedule(
      * @param metadata   meta data of new strand
      * @return Reference to the scheduled task
      */
-    public FutureValue schedule(Object[] params, Function<Object[], ?> function, @Nullable Strand parent, Callback callback,
-                                String strandName, @Nullable StrandMetadata metadata) {
+    public FutureValue schedule(Object[] params, Function<Object[], ?> function, @Nullable Strand parent,
+                                Callback callback, String strandName, @Nullable StrandMetadata metadata) {
         FutureValue future = createFuture(parent, callback, null, PredefinedTypes.TYPE_NULL, strandName, metadata);
         return schedule(params, function, future);
     }

bvm/ballerina-runtime/src/main/java/io/ballerina/runtime/internal/types/BFunctionType.java

@@ -40,7 +40,6 @@ public class BFunctionType extends BAnnotatableType implements FunctionType {
     @Nullable
     public Type retType;
     public long flags;
-    @Nullable
     public Parameter[] parameters;
 
     public BFunctionType(Module pkg) {
@@ -52,7 +51,7 @@ public BFunctionType(Module pkg) {
 
     public BFunctionType(Module pkg, long flags) {
         super("function", pkg, Object.class);
-        this.parameters = null;
+        this.parameters = new Parameter[0];
         this.retType = null;
         this.flags = flags;
     }

cli/ballerina-cli/src/main/java/io/ballerina/cli/cmd/CommandUtil.java

@@ -998,7 +998,6 @@ private static void initToolPackage(Path path, String packageName) throws IOExce
         Files.writeString(balToolToml, balToolManifest);
     }
 
-    @Nullable
     private static Optional<PackageVersion> findLatest(List<PackageVersion> packageVersions) {
         if (packageVersions.isEmpty()) {
             return Optional.empty();

compiler/ballerina-lang/src/main/java/io/ballerina/compiler/api/impl/ExpectedTypeFinder.java

@@ -1189,7 +1189,7 @@ private Optional<TypeSymbol> getExpectedTypeFromFunction(BLangNode bLangNode, To
         }
 
         if (langLibInvocation) {
-            if (bLangInvocation.expr.getBType().getKind() == TypeKind.ARRAY) {
+            if (bLangInvocation.expr != null && bLangInvocation.expr.getBType().getKind() == TypeKind.ARRAY) {
                 return Optional.ofNullable(typesFactory.getTypeDescriptor
                         (((BArrayType) bLangInvocation.expr.expectedType).eType));
             }

compiler/ballerina-lang/src/main/java/org/ballerinalang/spi/SystemPackageRepositoryProvider.java

@@ -18,7 +18,6 @@
 package org.ballerinalang.spi;
 
 import org.ballerinalang.repository.PackageRepository;
-import org.jetbrains.annotations.Nullable;
 import org.wso2.ballerinalang.compiler.packaging.repo.Repo;
 
 import java.net.URI;
@@ -32,12 +31,11 @@
  */
 public interface SystemPackageRepositoryProvider {
 
-    @Nullable
     static URI getClassUri(Object obj) {
         try {
             return obj.getClass().getProtectionDomain().getCodeSource().getLocation().toURI();
-        } catch (URISyntaxException ignore) {
-            return null;
+        } catch (URISyntaxException e) {
+            throw new RuntimeException("Error while getting the URI of the class", e);
         }
     }
 

compiler/ballerina-lang/src/main/java/org/wso2/ballerinalang/compiler/semantics/model/symbols/BInvokableSymbol.java

@@ -40,7 +40,6 @@
  */
 public class BInvokableSymbol extends BVarSymbol implements InvokableSymbol {
 
-    @Nullable
     public List<BVarSymbol> params;
     @Nullable
     public BVarSymbol restParam;

compiler/ballerina-lang/src/test/java/org/ballerinalang/toml/ManifestProcessorTest.java

@@ -167,7 +167,7 @@ public void testDependenciesIrregularPath() throws TomlException, IOException {
 
         Manifest manifest = ManifestProcessor.parseTomlContentFromString(this.validProjectBlock + "[dependencies] \n " +
                 "string-utils = {path = '" + balaPath + "', version = \"1.1.5\"} \n");
-        Path manifestPath = manifest.getDependencies().get(0).getMetadata().getPath();
+        Path manifestPath = manifest.getDependencies().get(0).getMetadata().getPath().orElseThrow();
         if (manifestPath.toString().contains("\\")) {
             manifestPath = Path.of(manifestPath.toString().replace("\\", "/"));
         } else {

compiler/ballerina-parser/src/main/java/io/ballerina/compiler/internal/parser/AbstractParserErrorHandler.java

@@ -25,6 +25,7 @@
 import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Objects;
 
 /**
  * Class to be extended by any parser error handler class.
@@ -159,7 +160,7 @@ private void validateSolution(Result bestMatch, ParserRuleContext currentCtx, ST
         }
 
         Solution firstFix = bestMatch.popFix();
-        Solution secondFix = bestMatch.peekFix();
+        Solution secondFix = bestMatch.peekFix().orElseThrow();
         bestMatch.pushFix(firstFix);
 
         if (secondFix.action == Action.REMOVE && secondFix.depth == 1) {
@@ -314,22 +315,20 @@ public void switchContext(ParserRuleContext context) {
      *
      * @return head of the stack
      */
-    @Nullable
     protected ParserRuleContext getParentContext() {
-        return this.ctxStack.peek();
+        return Objects.requireNonNull(this.ctxStack.peek());
     }
 
     /**
      * Returns the second element of the context stack.
      *
      * @return second element of the stack
      */
-    @Nullable
     protected ParserRuleContext getGrandParentContext() {
         ParserRuleContext parent = this.ctxStack.pop();
         ParserRuleContext grandParent = this.ctxStack.peek();
         this.ctxStack.push(parent);
-        return grandParent;
+        return Objects.requireNonNull(grandParent);
     }
 
     /**
@@ -422,8 +421,8 @@ protected Result seekInAlternativesPaths(int lookahead, int currentDepth, int cu
             }
 
             if (currentMatchRemoveFixes == bestMatchRemoveFixes) {
-                Solution currentSol = bestMatch.peekFix();
-                Solution foundSol = currentMatch.peekFix();
+                Solution currentSol = bestMatch.peekFix().orElseThrow();
+                Solution foundSol = currentMatch.peekFix().orElseThrow();
                 if (currentSol.action == Action.REMOVE && foundSol.action == Action.INSERT) {
                     bestMatch = currentMatch;
                 }
@@ -480,7 +479,7 @@ protected Result fixAndContinue(ParserRuleContext currentCtx, int lookahead, int
         // i.e: do not increment the match count by 1;
 
         if (isEntryPoint) {
-            fixedPathResult.solution = fixedPathResult.peekFix();
+            fixedPathResult.solution = fixedPathResult.peekFix().orElseThrow();
         } else {
             fixedPathResult.solution =
                     new Solution(Action.KEEP, currentCtx, getExpectedTokenKind(currentCtx), currentCtx.toString());

compiler/ballerina-parser/src/main/java/io/ballerina/compiler/internal/parser/BallerinaLexer.java

@@ -26,6 +26,7 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Objects;
 
 /**
  * A LL(k) lexer for ballerina.
@@ -45,7 +46,7 @@ public BallerinaLexer(CharReader charReader) {
      */
     @Override
     public STToken nextToken() {
-        STToken token = switch (this.mode) {
+        STToken token = switch (Objects.requireNonNull(this.mode, "Lexer mode was null, an underflow occurred")) {
             case TEMPLATE -> readTemplateToken();
             case REGEXP -> readRegExpTemplateToken();
             case INTERPOLATION -> {

compiler/ballerina-parser/src/main/java/io/ballerina/compiler/internal/parser/BallerinaParser.java

@@ -72,6 +72,7 @@
 import io.ballerina.compiler.syntax.tree.SyntaxKind;
 import io.ballerina.tools.diagnostics.DiagnosticCode;
 import io.ballerina.tools.text.CharReader;
+import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayDeque;
@@ -19016,12 +19017,12 @@ private List<STNode> getBindingPatternsList(List<STNode> ambibuousList, boolean
         return bindingPatterns;
     }
 
-    @Nullable
+    @Contract("null, _ -> null; !null, _ -> !null")
     private STNode getBindingPattern(STNode ambiguousNode, boolean isListBP) {
         DiagnosticCode errorCode = DiagnosticErrorCode.ERROR_INVALID_BINDING_PATTERN;
 
         if (isEmpty(ambiguousNode)) {
-            return ambiguousNode;
+            return null;
         }
 
         switch (ambiguousNode.kind) {

compiler/ballerina-parser/src/main/java/io/ballerina/compiler/internal/parser/BallerinaParserErrorHandler.java

@@ -854,7 +854,7 @@ public class BallerinaParserErrorHandler extends AbstractParserErrorHandler {
     private static final ParserRuleContext[] OPTIONAL_TOP_LEVEL_SEMICOLON =
             { ParserRuleContext.TOP_LEVEL_NODE, ParserRuleContext.SEMICOLON };
 
-  private static final ParserRuleContext[] TUPLE_MEMBER =
+    private static final ParserRuleContext[] TUPLE_MEMBER =
             { ParserRuleContext.ANNOTATIONS, ParserRuleContext.TYPE_DESC_IN_TUPLE };
 
     public BallerinaParserErrorHandler(@Nullable AbstractTokenReader tokenReader) {

compiler/ballerina-parser/src/main/java/io/ballerina/compiler/internal/parser/DocumentationLexer.java

@@ -28,6 +28,7 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
+import java.util.Objects;
 
 /**
  * A LL(k) lexer for documentation in ballerina.
@@ -63,7 +64,7 @@ public DocumentationLexer(CharReader charReader,
      */
     @Override
     public STToken nextToken() {
-        STToken token = switch (this.mode) {
+        STToken token = switch (Objects.requireNonNull(this.mode, "Lexer mode was null, an underflow occurred")) {
             case DOC_LINE_START_HASH -> {
                 processLeadingTrivia();
                 yield readDocLineStartHashToken();

compiler/ballerina-parser/src/main/java/io/ballerina/compiler/internal/parser/RegExpLexer.java

@@ -25,6 +25,7 @@
 import io.ballerina.tools.text.CharReader;
 
 import java.util.ArrayList;
+import java.util.Objects;
 
 /**
  * A LL(k) lexer for RegExp in ballerina.
@@ -45,7 +46,7 @@ public RegExpLexer(CharReader charReader) {
     @Override
     public STToken nextToken() {
         STToken token;
-        switch (this.mode) {
+        switch (Objects.requireNonNull(this.mode, "Lexer mode was null, an underflow occurred")) {
             case RE_DISJUNCTION:
             case RE_CHAR_CLASS:
                 token = readTokenInReDisjunction();

compiler/ballerina-parser/src/main/java/io/ballerina/compiler/internal/parser/Result.java

@@ -17,9 +17,8 @@
  */
 package io.ballerina.compiler.internal.parser;
 
-import org.jetbrains.annotations.Nullable;
-
 import java.util.ArrayDeque;
+import java.util.Optional;
 
 /**
  * Represent a result of a token-sequence-search in a sub-tree. The result will contain the fixes required to
@@ -58,9 +57,8 @@ public Result(ArrayDeque<AbstractParserErrorHandler.Solution> fixes, int matches
         this.matches = matches;
     }
 
-    @Nullable
-    protected AbstractParserErrorHandler.Solution peekFix() {
-        return this.fixes.peek();
+    protected Optional<AbstractParserErrorHandler.Solution> peekFix() {
+        return Optional.ofNullable(this.fixes.peek());
     }
 
     protected AbstractParserErrorHandler.Solution popFix() {

compiler/ballerina-parser/src/main/java/io/ballerina/compiler/internal/parser/XMLLexer.java

@@ -26,6 +26,7 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Objects;
 
 /**
  * A LL(k) lexer for XML in ballerina.
@@ -45,7 +46,7 @@ public XMLLexer(CharReader charReader) {
      */
     @Override
     public STToken nextToken() {
-        STToken token = switch (this.mode) {
+        STToken token = switch (Objects.requireNonNull(this.mode, "Lexer mode was null, an underflow occurred")) {
             case XML_CONTENT -> readTokenInXMLContent();
             case XML_ELEMENT_START_TAG -> {
                 processLeadingXMLTrivia();

compiler/ballerina-tools-api/src/main/java/io/ballerina/tools/text/LineMap.java

@@ -45,6 +45,9 @@ TextLine textLine(int line) {
     LinePosition linePositionFrom(int position) {
         positionRangeCheck(position);
         TextLine textLine = findLineFrom(position);
+        if (textLine == null) {
+            throw new IllegalArgumentException("Cannot find a line with the character offset '" + position + "'");
+        }
         return LinePosition.from(textLine.lineNo(), position - textLine.startOffset());
     }
 
@@ -98,7 +101,6 @@ private TextLine findLineFrom(int position) {
             return textLines[length - 1];
         }
 
-        TextLine foundTextLine = null;
         int left = 0;
         int right = length - 1;
         while (left <= right) {
@@ -109,14 +111,13 @@ private TextLine findLineFrom(int position) {
             int startOffset = textLines[middle].startOffset();
             int endOffset = textLines[middle].endOffsetWithNewLines();
             if (startOffset <= position && position < endOffset) {
-                foundTextLine = textLines[middle];
-                break;
+                return textLines[middle];
             } else if (endOffset <= position) {
                 left = middle + 1;
             } else {
                 right = middle - 1;
             }
         }
-        return foundTextLine;
+        return null;
     }
 }

language-server/modules/langserver-commons/src/main/java/org/ballerinalang/langserver/commons/toml/common/completion/TomlCompletionUtil.java

@@ -71,7 +71,8 @@ public static void fillNodeAtCursor(TomlCompletionContext context) {
         context.setCursorPositionInTree(txtPos);
         TextRange range = TextRange.from(txtPos, 0);
         NonTerminalNode nonTerminalNode = ((DocumentNode) st.get().rootNode()).findNode(range);
-        while (nonTerminalNode.parent() != null && !TomlSyntaxTreeUtil.withinTextRange(txtPos, nonTerminalNode)) {
+        while (nonTerminalNode != null &&
+                nonTerminalNode.parent() != null && !TomlSyntaxTreeUtil.withinTextRange(txtPos, nonTerminalNode)) {
             //Takes the top-level Node of the immediate cursor position
             nonTerminalNode = nonTerminalNode.parent();
         }

language-server/modules/langserver-core/src/main/java/org/ballerinalang/langserver/codeaction/providers/ExtractToLocalVarCodeAction.java

@@ -44,7 +44,6 @@
 import org.eclipse.lsp4j.Position;
 import org.eclipse.lsp4j.Range;
 import org.eclipse.lsp4j.TextEdit;
-import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -226,7 +225,6 @@ public String getName() {
         return NAME;
     }
 
-    @Nullable
     private Node getStatementNode(Node node) {
         Node statementNode = node;
         while (statementNode != null && !(statementNode instanceof StatementNode)