The failure was observed on *Ubuntu 22.04 aarch64*.

jtreg -v -testjdk:$JAVA_HOME test/jdk/java/awt/datatransfer/MimeFormatsTest.java

It was reproduced on *x86-64* as well.

The test java/awt/datatransfer/MimeFormatsTest.java intermittently fails with a custom toolkit with the following diagnostic:

====================8<--------------------
#section:main
----------messages:(7/269)----------
command: main MimeFormatsTest
reason: User specified action: run main MimeFormatsTest
started: Fri Nov 17 10:43:12 UTC 2023
Mode: othervm
Additional options from @modules: --add-modules java.desktop
finished: Fri Nov 17 10:43:13 UTC 2023
elapsed time (seconds): 1.049
----------configuration:(3/40)----------
Boot Layer
  add modules: java.desktop

----------System.out:(0/0)----------
----------System.err:(162/3536)----------
========= Child VM System.err ========
contents size=144
     char[0]=73
     char[1]=32
     char[2]=116
     char[3]=104
     char[4]=105
     char[5]=110
     char[6]=107
     char[7]=32
     char[8]=116
     char[9]=104
     char[10]=97
     char[11]=116
     char[12]=32
     char[13]=119
     char[14]=101
     char[15]=32
     char[16]=115
     char[17]=104
     char[18]=111
     char[19]=117
     char[20]=108
     char[21]=100
     char[22]=32
     char[23]=114
     char[24]=97
     char[25]=105
     char[26]=115
     char[27]=101
     char[28]=32
     char[29]=116
     char[30]=104
     char[31]=101
     char[32]=115
     char[33]=101
     char[34]=32
     char[35]=118
     char[36]=97
     char[37]=108
     char[38]=117
     char[39]=101
     char[40]=115
     char[41]=32
     char[42]=117
     char[43]=112
     char[44]=32
     char[45]=116
     char[46]=111
     char[47]=32
     char[48]=115
     char[49]=117
     char[50]=112
     char[51]=112
     char[52]=111
     char[53]=114
     char[54]=116
     char[55]=101
     char[56]=100
     char[57]=32
     char[58]=114
     char[59]=101
     char[60]=108
     char[61]=101
     char[62]=97
     char[63]=115
     char[64]=101
     char[65]=115
     char[66]=32
     char[67]=111
     char[68]=102
     char[69]=32
     char[70]=109
     char[71]=97
     char[72]=99
     char[73]=79
     char[74]=83
     char[75]=46
     char[76]=32
     char[77]=77
     char[78]=105
     char[79]=115
     char[80]=115
     char[81]=105
     char[82]=110
     char[83]=103
     char[84]=32
     char[85]=79
     char[86]=83
     char[87]=32
     char[88]=115
     char[89]=101
     char[90]=99
     char[91]=117
     char[92]=114
     char[93]=105
     char[94]=116
     char[95]=121
     char[96]=32
     char[97]=112
     char[98]=97
     char[99]=116
     char[100]=99
     char[101]=104
     char[102]=101
     char[103]=115
     char[104]=32
     char[105]=105
     char[106]=115
     char[107]=32
     char[108]=111
     char[109]=110
     char[110]=101
     char[111]=32
     char[112]=111
     char[113]=102
     char[114]=32
     char[115]=116
     char[116]=104
     char[117]=101
     char[118]=32
     char[119]=114
     char[120]=101
     char[121]=97
     char[122]=115
     char[123]=111
     char[124]=110
     char[125]=32
     char[126]=102
     char[127]=111
     char[128]=114
     char[129]=32
     char[130]=115
     char[131]=117
     char[132]=99
     char[133]=104
     char[134]=32
     char[135]=100
     char[136]=101
     char[137]=99
     char[138]=105
     char[139]=115
     char[140]=105
     char[141]=111
     char[142]=110
     char[143]=46
1700217793038 exit
Exiting
======================================
Child return code=0
java.lang.NullPointerException: Cannot invoke "String.length()" because "this.testData" is null
at MimeFormatsTest.start(MimeFormatsTest.java:174)
at MimeFormatsTest.main(MimeFormatsTest.java:220)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at com.sun.javatest.regtest.agent.MainWrapper$MainTask.run(MainWrapper.java:138)
at java.base/java.lang.Thread.run(Thread.java:1583)

JavaTest Message: Test threw exception: java.lang.NullPointerException: Cannot invoke "String.length()" because "this.testData" is null
JavaTest Message: shutting down test

STATUS:Failed.`main' threw exception: java.lang.NullPointerException: Cannot invoke "String.length()" because "this.testData" is null
====================8<--------------------