question: protected < H extends MemHolder < ? extends CommonAllocator < ? > , ? , ? > > H create ( MemCreate < H > creator , PerformanceLevel startlevel , long size ) { H ret = null ; boolean eligible = false ; for ( PerformanceLevel lvl : m_info . keySet ( ) ) { if ( ! eligible && startlevel == lvl ) { eligible = true ; } if ( eligible ) { int distance = 0 ; List < CommonAllocator < ? > > bmas = m_info . get ( lvl ) ; for ( CommonAllocator < ? > bma : bmas ) { ret = creator . create ( bma , size ) ; if ( null == ret ) { distance ++ ; } else { if ( null != m_bwlvlchange && m_prevbwlevel != lvl ) { m_bwlvlchange . changed ( m_prevbwlevel , lvl ) ; m_prevbwlevel = lvl ; } if ( null != m_allocatorChange && m_prevallocator != bma ) { m_allocatorChange . changed ( lvl , m_prevallocator , bma ) ; m_prevallocator = bma ; } break ; } } Collections . rotate ( bmas , distance ) ; } if ( null != ret ) { break ; } } return ret ; }
target:  a factory to create memory resource.