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Groovy example source code file (ReturnAdder.java)

This example Groovy source code file (ReturnAdder.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Groovy tags/keywords

blockstatement, blockstatement, bytecodesequence, expressionstatement, expressionstatement, ifstatement, list, returnstatement, returnstatement, statement, statement, synchronizedstatement, trycatchstatement, util, variablescope

The Groovy ReturnAdder.java source code

/*
 * Copyright 2003-2008 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.codehaus.groovy.classgen;

import org.codehaus.groovy.ast.ClassHelper;
import org.codehaus.groovy.ast.MethodNode;
import org.codehaus.groovy.ast.VariableScope;
import org.codehaus.groovy.ast.expr.ConstantExpression;
import org.codehaus.groovy.ast.expr.Expression;
import org.codehaus.groovy.ast.stmt.*;

import java.util.List;
import java.util.ArrayList;

/**
 * Utility class to add return statements.
 * Extracted from Verifier as it can be useful for some AST transformations
 */
public class ReturnAdder {
    public static void addReturnIfNeeded(MethodNode node) {
        Statement statement = node.getCode();
        if (!node.isVoidMethod()) {
            if (statement != null) // it happens with @interface methods
              node.setCode(addReturnsIfNeeded(statement, node.getVariableScope()));
        } else if (!node.isAbstract() && node.getReturnType().redirect()!=ClassHelper.VOID_TYPE) {
            if (!(statement instanceof BytecodeSequence)) {
                BlockStatement newBlock = new BlockStatement();
                Statement code = node.getCode();
                if (code instanceof BlockStatement) {
                    newBlock.setVariableScope(((BlockStatement) code).getVariableScope());
                }
                if (statement instanceof BlockStatement) {
                    newBlock.addStatements(((BlockStatement)statement).getStatements());
                } else {
                    newBlock.addStatement(statement);
                }
                newBlock.addStatement(ReturnStatement.RETURN_NULL_OR_VOID);
                newBlock.setSourcePosition(statement);
                node.setCode(newBlock);
            }
        }
    }

    private static Statement addReturnsIfNeeded(Statement statement, VariableScope scope) {
        if (  statement instanceof ReturnStatement
           || statement instanceof BytecodeSequence
           || statement instanceof ThrowStatement)
        {
            return statement;
        }

        if (statement instanceof EmptyStatement) {
            return new ReturnStatement(ConstantExpression.NULL);
        }

        if (statement instanceof ExpressionStatement) {
            ExpressionStatement expStmt = (ExpressionStatement) statement;
            Expression expr = expStmt.getExpression();
            ReturnStatement ret = new ReturnStatement(expr);
            ret.setSourcePosition(expr);
            ret.setStatementLabel(statement.getStatementLabel());
            return ret;
        }

        if (statement instanceof SynchronizedStatement) {
            SynchronizedStatement sync = (SynchronizedStatement) statement;
            sync.setCode(addReturnsIfNeeded(sync.getCode(), scope));
            return sync;
        }

        if (statement instanceof IfStatement) {
            IfStatement ifs = (IfStatement) statement;
            ifs.setIfBlock(addReturnsIfNeeded(ifs.getIfBlock(), scope));
            ifs.setElseBlock(addReturnsIfNeeded(ifs.getElseBlock(), scope));
            return ifs;
        }

        if (statement instanceof SwitchStatement) {
            SwitchStatement swi = (SwitchStatement) statement;
            for (CaseStatement caseStatement : swi.getCaseStatements()) {
                caseStatement.setCode(adjustSwitchCaseCode(caseStatement.getCode(), scope, false));
            }
            swi.setDefaultStatement(adjustSwitchCaseCode(swi.getDefaultStatement(), scope, true)); 
            return swi;
        }

        if (statement instanceof TryCatchStatement) {
            TryCatchStatement trys = (TryCatchStatement) statement;
            trys.setTryStatement(addReturnsIfNeeded(trys.getTryStatement(), scope));
            final int len = trys.getCatchStatements().size();
            for (int i = 0; i != len; ++i) {
                final CatchStatement catchStatement = trys.getCatchStatement(i);
                catchStatement.setCode(addReturnsIfNeeded(catchStatement.getCode(), scope));
            }
            return trys;
        }

        if (statement instanceof BlockStatement) {
            BlockStatement block = (BlockStatement) statement;

            final List list = block.getStatements();
            if (!list.isEmpty()) {
                int idx = list.size() - 1;
                Statement last = addReturnsIfNeeded((Statement) list.get(idx), block.getVariableScope());
                list.set(idx, last);
                if (!statementReturns(last)) {
                    list.add(new ReturnStatement(ConstantExpression.NULL));
                }
            } else {
                ReturnStatement ret = new ReturnStatement(ConstantExpression.NULL);
                ret.setSourcePosition(block);
                return ret;
            }

            BlockStatement newBlock = new BlockStatement(list, block.getVariableScope());
            newBlock.setSourcePosition(block);
            return newBlock;
        }

        if (statement == null) {
            return new ReturnStatement(ConstantExpression.NULL);
        } else {
            final List list = new ArrayList();
            list.add(statement);
            list.add(new ReturnStatement(ConstantExpression.NULL));

            BlockStatement newBlock = new BlockStatement(list, new VariableScope(scope));
            newBlock.setSourcePosition(statement);
            return newBlock;
        }
    }

    private static Statement adjustSwitchCaseCode(Statement statement, VariableScope scope, boolean defaultCase) {
        if(statement instanceof BlockStatement) {
            final List list = ((BlockStatement)statement).getStatements();
            if (!list.isEmpty()) {
                int idx = list.size() - 1;
                Statement last = (Statement) list.get(idx);
                if(last instanceof BreakStatement) {
                    list.remove(idx);
                    return addReturnsIfNeeded(statement, scope);
                } else if(defaultCase) {
                    return addReturnsIfNeeded(statement, scope);
                }
            }
        }
        return statement;
    }

    private static boolean statementReturns(Statement last) {
        return (
                last instanceof ReturnStatement ||
                last instanceof BlockStatement ||
                last instanceof IfStatement ||
                last instanceof ExpressionStatement ||
                last instanceof EmptyStatement ||
                last instanceof TryCatchStatement ||
                last instanceof BytecodeSequence ||
                last instanceof ThrowStatement ||
                last instanceof SynchronizedStatement
                );
    }
}

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