The jars shipped with the Eclipse bundle "Appian Developer Edition" are very old and the documented public API differs in some cases from what is actually available.
For example the 19.4 javadocs expose com.appiancorp.suiteapi.applications.Application method getObjectsByType(java.lang.Long appianTypeLong) but the jars available in Eclipse only support the deprecated method getObjectsByType(Type<H,I,U>
For this particular problem the jar bundled with Eclipse is appian-suiteapi.jar. The closes equivalent jar I can find in the 19.4 binaries appian-suiteapi-22.214.171.124.jar does not contain the required package.
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The issue you are facing has been reported to the Product team, and we have published a KB article for the current workaround for this @Type notation not being available:
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