Mockito模拟最终类的静态方法并不总是有效

Question

设置：

两个类都以静态方法结尾：UUID（java），BUKKIT（spigot-api）。

import org.bukkit.Bukkit;
import org.bukkit.entity.Player;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

import java.util.UUID;

import static org.junit.Assert.assertEquals;
import static org.powermock.api.mockito.PowerMockito.when;

/**
 * TempTest.
 */
@RunWith(PowerMockRunner.class)
@PrepareForTest({Bukkit.class, UUID.class})
public class TempTest {

    @Mock
    private Player player;

    private UUID uuid = UUID.fromString("6ba38d11-e901-4d81-950b-d9743e4a98fa");

    @Before
    public void setUp() {
        MockitoAnnotations.initMocks(this);
        PowerMockito.mockStatic(Bukkit.class, UUID.class);
    }

    @Test
    public void testPlayer() {
        when(Bukkit.getPlayer("test")).thenReturn(player);
        Player actualPlayer = Bukkit.getPlayer("test");

        assertEquals(player, actualPlayer);
    }

    @Test
    public void testUuid() {
        when(UUID.randomUUID()).thenReturn(uuid);
        UUID actualUuid = UUID.randomUUID();
        assertEquals(uuid, actualUuid);
    }
}

第一个测试工作正常，第二个测试在代码的第一行失败：

org.mockito.exceptions.base.MockitoException: 
Cannot mock/spy class java.util.UUID
Mockito cannot mock/spy because :
 - final class

    at com.gmail.nodondarkeye.plugintutorial.TempTest.testUuid(TempTest.java:47)

问题：

为什么一个测试失败而另一个没有失败。只是似乎找不到明显的区别，而且我的测试代码也没有看到任何错误。欢迎所有见解。