java.lang.OutOfMemoryError without org.gradle.parallel=true

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1

I faced very strange issue. some our CI build system occurs follows errors :
java.lang.OutOfMemoryError: Java heap space

    at sun.text.resources.FormatData.getContents(FormatData.java:122)

    at sun.util.resources.ParallelListResourceBundle.loadLookupTablesIfNecessary(ParallelListResourceBundle.java:168)

    at sun.util.resources.ParallelListResourceBundle.handleKeySet(ParallelListResourceBundle.java:134)

    at sun.util.resources.ParallelListResourceBundle.keySet(ParallelListResourceBundle.java:143)

    at sun.util.resources.ParallelListResourceBundle.containsKey(ParallelListResourceBundle.java:129)

    at sun.util.resources.ParallelListResourceBundle$KeySet.contains(ParallelListResourceBundle.java:208)

    at sun.util.resources.ParallelListResourceBundle.containsKey(ParallelListResourceBundle.java:129)

    at sun.util.locale.provider.LocaleResources.getDecimalFormatSymbolsData(LocaleResources.java:182)

    at java.text.DecimalFormatSymbols.initialize(DecimalFormatSymbols.java:616)

    at java.text.DecimalFormatSymbols.<init>(DecimalFormatSymbols.java:113)

    at sun.util.locale.provider.DecimalFormatSymbolsProviderImpl.getInstance(DecimalFormatSymbolsProviderImpl.java:85)

    at java.text.DecimalFormatSymbols.getInstance(DecimalFormatSymbols.java:180)

    at java.util.Formatter.getZero(Formatter.java:2283)

    at java.util.Formatter.<init>(Formatter.java:1892)

    at java.util.Formatter.<init>(Formatter.java:1914)

    at java.lang.String.format(String.java:2940)

    at org.gradle.internal.remote.internal.inet.SocketConnection.receive(SocketConnection.java:94)

    at org.gradle.launcher.daemon.client.DaemonClientConnection.receive(DaemonClientConnection.java:77)

    at org.gradle.launcher.daemon.client.DaemonClientConnection.receive(DaemonClientConnection.java:35)

    at org.gradle.launcher.daemon.client.DaemonClient.monitorBuild(DaemonClient.java:216)

    at org.gradle.launcher.daemon.client.DaemonClient.executeBuild(DaemonClient.java:185)

    at org.gradle.launcher.daemon.client.DaemonClient.execute(DaemonClient.java:148)

    at org.gradle.launcher.daemon.client.DaemonClient.execute(DaemonClient.java:99)

    at org.gradle.launcher.cli.RunBuildAction.run(RunBuildAction.java:56)

    at org.gradle.internal.Actions$RunnableActionAdapter.execute(Actions.java:212)

    at org.gradle.launcher.cli.DefaultCommandLineActionFactory$ParseAndBuildAction.execute(DefaultCommandLineActionFactory.java:294)

    at org.gradle.launcher.cli.DefaultCommandLineActionFactory$ParseAndBuildAction.execute(DefaultCommandLineActionFactory.java:266)

    at org.gradle.launcher.cli.DebugLoggerWarningAction.execute(DebugLoggerWarningAction.java:82)

    at org.gradle.launcher.cli.DebugLoggerWarningAction.execute(DebugLoggerWarningAction.java:30)

When I add “org.gradle.parallel=true” to gradle.properties,
This error is magically gone.

I want to know what affects this and what is main reason of this issue.