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synchronized ?????????

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public class SynchronizedMethod {    private int sum;    public int getSum() {        return sum;    }    public void setSum(int sum) {        this.sum = sum;    }    public void calculate() {        setSum(getSum() + 1);    }}

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class SynchronizedMethodTest {    @Test    void calculate() throws InterruptedException {        ExecutorService service = Executors.newFixedThreadPool(3);        SynchronizedMethod summation = new SynchronizedMethod();        IntStream.range(0, 1000)                .forEach(count -> service.submit(summation::calculate));        service.awaitTermination(1000, TimeUnit.MILLISECONDS);        assertEquals(1000, summation.getSum());    }}

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synchronized ???????

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public synchronized void synchronizedCalculate() {    setSum(getSum() + 1);}

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@Testvoid synchronizedCalculate() throws InterruptedException {    ExecutorService service = Executors.newFixedThreadPool(3);    SynchronizedMethod summation = new SynchronizedMethod();    IntStream.range(0, 1000)            .forEach(count -> service.submit(summation::synchronizedCalculate));    service.awaitTermination(1000, TimeUnit.MILLISECONDS);    assertEquals(1000, summation.getSum());}

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2. ?? static ???

public class SynchronizedStaticMethod {    public static int sum;    public synchronized static void synchronizedCalculate() {        sum = sum + 1;    }}

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class SynchronizedStaticMethodTest {    @Test    void synchronizedCalculate() throws InterruptedException {        ExecutorService service = Executors.newFixedThreadPool(3);        IntStream.range(0, 1000)                .forEach(count -> service.submit(SynchronizedStaticMethod::synchronizedCalculate));        service.awaitTermination(1000, TimeUnit.MILLISECONDS);        assertEquals(1000, SynchronizedStaticMethod.sum);    }}

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3. ??????

public void synchronisedThis() {    synchronized (this) {        setSum(getSum() + 1);    }}

?????????????????? synchronized ?????????????

public static void synchronisedThis() {    synchronized (SynchronizedStaticMethod.class) {        sum = sum + 1;    }}

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@Testvoid synchronisedThis() throws InterruptedException {    ExecutorService service = Executors.newFixedThreadPool(3);    SynchronizedMethod summation = new SynchronizedMethod();    IntStream.range(0, 1000)            .forEach(count -> service.submit(summation::synchronisedThis));    service.awaitTermination(1000, TimeUnit.MILLISECONDS);    assertEquals(1000, summation.getSum());}

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