Java8 lambda：按相反的顺序对流进行排序？

时间：2018-06-01 14:40:18

标签： lambda collections java-8 functional-programming java-stream

我有这个列表，我想按预订顺序订购，但我在自动完成帮助中找不到任何.reversed()功能

 myMenus(user)
                .stream()
                .filter(mps ->  mps.get1PercentageChange() > 0 &&
                                mps.get2PercentageChange() > 0 &&
                                mps.get3PercentageChange() > 0 &
                                mps.get4PercentageChange() > 0)
                .sorted(comparing(mps -> mps.getDailyPercentageChange()))
                .collect(toList());

我也尝试过：

myMenus(user)
        .stream()
        .filter(mps ->  mps.get1PercentageChange() > 0 &&
                        mps.get2PercentageChange() > 0 &&
                        mps.get3PercentageChange() > 0 &
                        mps.get4PercentageChange() > 0)
        .sorted(comparing(mps -> mps.getDailyPercentageChange()).reversed())
        .collect(toList());

然后我有编译错误：

Cannot infer type argument(s) for <T, U> comparing(Function<? super T,? 
     extends U>)

2 个答案:

答案 0 :(得分：5)

Comparator有一个reversed方法来获得反向排序，所以：

.sorted(comparing(mps -> mps.getDailyPercentageChange()).reversed())

应该有用。

答案 1 :(得分：4)

这是一种类型推断问题。您需要帮助编译器。

你可以尝试一些事情：

FAILURE: Build failed with an exception.

* Where:
Build file '/Users/userx/AndroidStudioProjects/GarageTinker/app/build.gradle' line: 1

* What went wrong:
A problem occurred evaluating project ':app'.
> Failed to apply plugin [id 'com.android.application']
   > Minimum supported Gradle version is 4.4. Current version is 4.1. If using the gradle wrapper, try editing the distributionUrl in /Users/userx/AndroidStudioProjects/GarageTinker/gradle/wrapper/gradle-wrapper.properties to gradle-4.4-all.zip

* Try:
Run with --info or --debug option to get more log output.


    Exception is:
    org.gradle.api.GradleScriptException: A problem occurred evaluating project ':app'.
            at org.gradle.groovy.scripts.internal.DefaultScriptRunnerFactory$ScriptRunnerImpl.run(DefaultScriptRunnerFactory.java:92)
            at org.gradle.configuration.DefaultScriptPluginFactory$ScriptPluginImpl$2.run(DefaultScriptPluginFactory.java:187)
            at org.gradle.configuration.ProjectScriptTarget.addConfiguration(ProjectScriptTarget.java:77)
            at org.gradle.configuration.DefaultScriptPluginFactory$ScriptPluginImpl.apply(DefaultScriptPluginFactory.java:192)
            at org.gradle.configuration.BuildOperationScriptPlugin$1.run(BuildOperationScriptPlugin.java:61)
            at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
            at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
            at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:197)
            at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:107)
            at org.gradle.configuration.BuildOperationScriptPlugin.apply(BuildOperationScriptPlugin.java:58)
            at org.gradle.configuration.project.BuildScriptProcessor.execute(BuildScriptProcessor.java:39)
            at org.gradle.configuration.project.BuildScriptProcessor.execute(BuildScriptProcessor.java:26)
            at org.gradle.configuration.project.ConfigureActionsProjectEvaluator.evaluate(ConfigureActionsProjectEvaluator.java:34)
            at org.gradle.configuration.project.LifecycleProjectEvaluator.doConfigure(LifecycleProjectEvaluator.java:63)
            at org.gradle.configuration.project.LifecycleProjectEvaluator.access$100(LifecycleProjectEvaluator.java:33)
            at org.gradle.configuration.project.LifecycleProjectEvaluator$ConfigureProject.run(LifecycleProjectEvaluator.java:103)
            at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
            at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
            at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:197)
            at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:107)
            at org.gradle.configuration.project.LifecycleProjectEvaluator.evaluate(LifecycleProjectEvaluator.java:49)
            at org.gradle.api.internal.project.DefaultProject.evaluate(DefaultProject.java:651)
            at org.gradle.api.internal.project.DefaultProject.evaluate(DefaultProject.java:133)
            at org.gradle.execution.TaskPathProjectEvaluator.configure(TaskPathProjectEvaluator.java:35)
            at org.gradle.execution.TaskPathProjectEvaluator.configureHierarchy(TaskPathProjectEvaluator.java:62)
            at org.gradle.configuration.DefaultBuildConfigurer.configure(DefaultBuildConfigurer.java:38)
            at org.gradle.initialization.DefaultGradleLauncher$ConfigureBuild.run(DefaultGradleLauncher.java:246)
            at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
            at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
            at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:197)
            at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:107)
            at org.gradle.initialization.DefaultGradleLauncher.configureBuild(DefaultGradleLauncher.java:165)
            at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:124)
                at org.gradle.initialization.DefaultGradleLauncher.executeTasks(DefaultGradleLauncher.java:107)
                at org.gradle.internal.invocation.GradleBuildController$1.call(GradleBuildController.java:78)
                at org.gradle.internal.invocation.GradleBuildController$1.call(GradleBuildController.java:75)
                at org.gradle.internal.work.DefaultWorkerLeaseService.withLocks(DefaultWorkerLeaseService.java:152)
                at org.gradle.internal.invocation.GradleBuildController.doBuild(GradleBuildController.java:100)
                at org.gradle.internal.invocation.GradleBuildController.run(GradleBuildController.java:75)
                at org.gradle.tooling.internal.provider.ExecuteBuildActionRunner.run(ExecuteBuildActionRunner.java:28)
                at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)
                at org.gradle.tooling.internal.provider.ValidatingBuildActionRunner.run(ValidatingBuildActionRunner.java:32)
                at org.gradle.launcher.exec.RunAsBuildOperationBuildActionRunner$1.run(RunAsBuildOperationBuildActionRunner.java:43)
                at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
                at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
                at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:197)
                at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:107)
                at org.gradle.launcher.exec.RunAsBuildOperationBuildActionRunner.run(RunAsBuildOperationBuildActionRunner.java:40)
                at org.gradle.tooling.internal.provider.SubscribableBuildActionRunner.run(SubscribableBuildActionRunner.java:51)
                at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:45)
                at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:29)
                at org.gradle.launcher.exec.BuildTreeScopeBuildActionExecuter.execute(BuildTreeScopeBuildActionExecuter.java:39)
                at org.gradle.launcher.exec.BuildTreeScopeBuildActionExecuter.execute(BuildTreeScopeBuildActionExecuter.java:25)
                at org.gradle.tooling.internal.provider.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:71)
                at org.gradle.tooling.internal.provider.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:45)
                at org.gradle.tooling.internal.provider.ServicesSetupBuildActionExecuter.execute(ServicesSetupBuildActionExecuter.java:51)
                at org.gradle.tooling.internal.provider.ServicesSetupBuildActionExecuter.execute(ServicesSetupBuildActionExecuter.java:32)
                at org.gradle.tooling.internal.provider.GradleThreadBuildActionExecuter.execute(GradleThreadBuildActionExecuter.java:36)
                at org.gradle.tooling.internal.provider.GradleThreadBuildActionExecuter.execute(GradleThreadBuildActionExecuter.java:25)
                at org.gradle.tooling.internal.provider.ParallelismConfigurationBuildActionExecuter.execute(ParallelismConfigurationBuildActionExecuter.java:43)
                at org.gradle.tooling.internal.provider.ParallelismConfigurationBuildActionExecuter.execute(ParallelismConfigurationBuildActionExecuter.java:29)
                at org.gradle.tooling.internal.provider.StartParamsValidatingActionExecuter.execute(StartParamsValidatingActionExecuter.java:64)
                at org.gradle.tooling.internal.provider.StartParamsValidatingActionExecuter.execute(StartParamsValidatingActionExecuter.java:29)
                at org.gradle.tooling.internal.provider.SessionFailureReportingActionExecuter.execute(SessionFailureReportingActionExecuter.java:55)
                at org.gradle.tooling.internal.provider.SessionFailureReportingActionExecuter.execute(SessionFailureReportingActionExecuter.java:42)
                at org.gradle.tooling.internal.provider.SetupLoggingActionExecuter.execute(SetupLoggingActionExecuter.java:58)
                at org.gradle.tooling.internal.provider.SetupLoggingActionExecuter.execute(SetupLoggingActionExecuter.java:33)
                at org.gradle.launcher.daemon.server.exec.ExecuteBuild.doBuild(ExecuteBuild.java:67)
                at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
                at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
                at org.gradle.launcher.daemon.server.exec.WatchForDisconnection.execute(WatchForDisconnection.java:37)
                at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
                at org.gradle.launcher.daemon.server.exec.ResetDeprecationLogger.execute(ResetDeprecationLogger.java:26)
                at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
                at org.gradle.launcher.daemon.server.exec.RequestStopIfSingleUsedDaemon.execute(RequestStopIfSingleUsedDaemon.java:34)
                at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
                at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:74)
                at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:72)
                at org.gradle.util.Swapper.swap(Swapper.java:38)
                at org.gradle.launcher.daemon.server.exec.ForwardClientInput.execute(ForwardClientInput.java:72)
                at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
                at org.gradle.launcher.daemon.server.exec.LogAndCheckHealth.execute(LogAndCheckHealth.java:55)
                at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
                at org.gradle.launcher.daemon.server.exec.LogToClient.doBuild(LogToClient.java:62)
                at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
                at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
                at org.gradle.launcher.daemon.server.exec.EstablishBuildEnvironment.doBuild(EstablishBuildEnvironment.java:82)
                at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
                at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
                at org.gradle.launcher.daemon.server.exec.StartBuildOrRespondWithBusy$1.run(StartBuildOrRespondWithBusy.java:50)
                at org.gradle.launcher.daemon.server.DaemonStateCoordinator$1.run(DaemonStateCoordinator.java:297)
                at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
                at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:46)
                at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
        Caused by: org.gradle.api.internal.plugins.PluginApplicationException: Failed to apply plugin [id 'com.android.application']
                at org.gradle.api.internal.plugins.DefaultPluginManager.doApply(DefaultPluginManager.java:150)
                at org.gradle.api.internal.plugins.DefaultPluginManager.apply(DefaultPluginManager.java:125)
                at org.gradle.api.internal.plugins.DefaultObjectConfigurationAction.applyType(DefaultObjectConfigurationAction.java:113)
                at org.gradle.api.internal.plugins.DefaultObjectConfigurationAction.access$200(DefaultObjectConfigurationAction.java:36)
                at org.gradle.api.internal.plugins.DefaultObjectConfigurationAction$3.run(DefaultObjectConfigurationAction.java:80)
                at org.gradle.api.internal.plugins.DefaultObjectConfigurationAction.execute(DefaultObjectConfigurationAction.java:136)
                at org.gradle.api.internal.project.AbstractPluginAware.apply(AbstractPluginAware.java:46)
                at org.gradle.api.internal.project.ProjectScript.apply(ProjectScript.java:34)
                at org.gradle.api.Script$apply$0.callCurrent(Unknown Source)
                at build_2kqgzlfuw508yc8aqt2bik9zq.run(/Users/userx/AndroidStudioProjects/GarageTinker/app/build.gradle:1)
                at org.gradle.groovy.scripts.internal.DefaultScriptRunnerFactory$ScriptRunnerImpl.run(DefaultScriptRunnerFactory.java:90)
                ... 93 more
        Caused by: java.lang.RuntimeException: Minimum supported Gradle version is 4.4. Current version is 4.1. If using the gradle wrapper, try editing the distributionUrl in /Users/userx/AndroidStudioProjects/GarageTinker/gradle/wrapper/gradle-wrapper.properties to gradle-4.4-all.zip
                at com.android.build.gradle.BasePlugin.checkGradleVersion(BasePlugin.java:682)
                at com.android.build.gradle.BasePlugin.configureProject(BasePlugin.java:341)
                at com.android.builder.profile.ThreadRecorder.record(ThreadRecorder.java:81)
                at com.android.build.gradle.BasePlugin.apply(BasePlugin.java:277)
                at com.android.build.gradle.AppPlugin.apply(AppPlugin.java:120)
                at com.android.build.gradle.AppPlugin.apply(AppPlugin.java:47)
                at org.gradle.api.internal.plugins.ImperativeOnlyPluginTarget.applyImperative(ImperativeOnlyPluginTarget.java:42)
                at org.gradle.api.internal.plugins.RuleBasedPluginTarget.applyImperative(RuleBasedPluginTarget.java:50)
                at org.gradle.api.internal.plugins.DefaultPluginManager.addPlugin(DefaultPluginManager.java:165)
                at org.gradle.api.internal.plugins.DefaultPluginManager.access$200(DefaultPluginManager.java:47)
                at org.gradle.api.internal.plugins.DefaultPluginManager$AddPluginBuildOperation.run(DefaultPluginManager.java:252)
                at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)
                at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)
                at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:197)
                at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:107)
                at org.gradle.api.internal.plugins.DefaultPluginManager.doApply(DefaultPluginManager.java:144)
                ... 103 more

或

.sorted(comparing(T::getDailyPercentageChange).reversed())

.sorted(comparing((T mps) -> mps.getDailyPercentageChange()).reversed()) 是被比较元素的类型。

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