java8以前时间api线程不安全问题

旧城等待， 2021-12-20 08:11 102阅读 0赞

java8以前时间api是线程不安全的，可以在本地写一个线程进行测试，会出现以下异常！

package com.cdy.java801.test;
    
    import java.text.SimpleDateFormat;
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.List;
    import java.util.concurrent.*;
    
    public class TestSimpleDateFormat {
    
        public static void main(String[] args) throws ExecutionException, InterruptedException {
            SimpleDateFormat format = new SimpleDateFormat("YYYY-MM-DD");
    
            ExecutorService pool = Executors.newFixedThreadPool(10);
            List<Future<Date>> futures = new ArrayList<>();
            try {
    
                Callable<Date> call = new Callable<Date>() {
                    @Override
                    public Date call() throws Exception {
                        return format.parse("2019-06-28");
                    }
                };
    
                /*Callable<Date> call = new Callable<Date>() {
                    @Override
                    public Date call() throws Exception {
                        return SimpleDateFormatLocal.convert("2019-06-28");
                    }
                };*/
                for (int i =0;i < 100 ;i++) {
                    futures.add(pool.submit(call));
                }
                System.out.println("--------------------------");
    
            }catch (Exception e) {
                e.printStackTrace();
            }finally {
                pool.shutdown();
            }
            futures.stream().map(TestSimpleDateFormat::apply).forEach(System.out::println);
    
        }
    
        private static Date apply(Future<Date> e) {
            Date date = null;
            try {
                date = e.get();
            } catch (InterruptedException ex) {
                ex.printStackTrace();
            } catch (ExecutionException ex) {
                ex.printStackTrace();
            }
            return date;
        }
    }

异常：

java.util.concurrent.ExecutionException: java.lang.NumberFormatException: For input string: "E20194"
    	at java.util.concurrent.FutureTask.report(FutureTask.java:122)
    	at java.util.concurrent.FutureTask.get(FutureTask.java:192)
    	at com.cdy.java801.test.TestSimpleDateFormat.apply(TestSimpleDateFormat.java:48)
    	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
    	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1374)
    	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
    	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
    	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
    	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
    	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    	at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
    	at com.cdy.java801.test.TestSimpleDateFormat.main(TestSimpleDateFormat.java:41)
    Caused by: java.lang.NumberFormatException: For input string: "E20194"
    	at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2043)
    	at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
    	at java.lang.Double.parseDouble(Double.java:538)
    	at java.text.DigitList.getDouble(DigitList.java:169)
    	at java.text.DecimalFormat.parse(DecimalFormat.java:2056)
    	at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:1869)
    	at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)
    	at java.text.DateFormat.parse(DateFormat.java:364)
    	at com.cdy.java801.test.TestSimpleDateFormat$1.call(TestSimpleDateFormat.java:21)
    	at com.cdy.java801.test.TestSimpleDateFormat$1.call(TestSimpleDateFormat.java:18)
    	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    	at java.lang.Thread.run(Thread.java:745)
    null

解决办法，使用java 自带的 ThreadLocal类，对时间api进行封装，解决并发问题

package com.cdy.java801.test;
    
    import java.text.SimpleDateFormat;
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.List;
    import java.util.concurrent.*;
    
    public class TestSimpleDateFormat {
    
        public static void main(String[] args) throws ExecutionException, InterruptedException {
            SimpleDateFormat format = new SimpleDateFormat("YYYY-MM-DD");
    
            ExecutorService pool = Executors.newFixedThreadPool(10);
            List<Future<Date>> futures = new ArrayList<>();
            try {
    
                /*Callable<Date> call = new Callable<Date>() {
                    @Override
                    public Date call() throws Exception {
                        return format.parse("2019-06-28");
                    }
                };*/
    
                Callable<Date> call = new Callable<Date>() {
                    @Override
                    public Date call() throws Exception {
                        return SimpleDateFormatLocal.convert("2019-06-28");
                    }
                };
                for (int i =0;i < 100 ;i++) {
                    futures.add(pool.submit(call));
                }
                System.out.println("--------------------------");
    
            }catch (Exception e) {
                e.printStackTrace();
            }finally {
                pool.shutdown();
            }
            futures.stream().map(TestSimpleDateFormat::apply).forEach(System.out::println);
    
        }
    
        private static Date apply(Future<Date> e) {
            Date date = null;
            try {
                date = e.get();
            } catch (InterruptedException ex) {
                ex.printStackTrace();
            } catch (ExecutionException ex) {
                ex.printStackTrace();
            }
            return date;
        }
    }

package com.cdy.java801.test;
    
    import java.text.DateFormat;
    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.Date;
    
    public class SimpleDateFormatLocal {
    
        private static final ThreadLocal<DateFormat> df = new ThreadLocal<DateFormat>(){
    
            protected DateFormat initialValue(){
                return  new SimpleDateFormat("YYYY-mm-DD");
            }
        };
    
        public static Date convert(String str) throws ParseException {
            return  df.get().parse(str);
        }
    
    }