$20(20),$ char $.$ true, $,,,$ false. $$: false Sample run char$[]$ in $=\{$I$\text{'},$ a$\text{'},\text{'}$v$\text{'},\text{'}$a$\text{'},\text{'}\text{'},\text{'}1\text{'},\text{'}3\text{'}\}$; $|=$ isValidArray$($in$)$; System.out.println$("$:$"+)$; char$[]$ in $=\{\text{'}$C$\text{'},\text{'}+\text{'},\text{'}+?,),1\text{'},\text{'}1\text{'}\}$; $=$ isValidArray$($in$)$; System.out.println$("$:$"+)$; char$[]$ in $=\{\text{'}$T$\text{'},\text{'}$a$\text{'},\text{'}$v$\text{'},\text{'}$a$\text{'},\text{'},\text{'}$T$\text{'},3\text{'},\text{'}1,5\%$; $=$ isValidArray$($in$)$; System.out.println$("$: $"+)$; $$ XC$20$: $$: $$