Check Java is present before installing

Question

I\'m creating an Inno Setup installer for a jar app. What I want to do right now is to check if java is present before proceeding with the install. So I only need to be sure the

Answer 1

More enhancement for the already defined code:

1. Check for existence of JRE / JDK.
2. Verify in either 32bit or 64bit view of registry.

Code:

function InitializeSetup(): Boolean;
var
 ErrorCode: Integer;
 JavaInstalled : Boolean;
 ResultMsg : Boolean;
 Versions: TArrayOfString;
 I: Integer;
 regRoot: Integer;
begin
 // Check which view of registry should be taken:
 regRoot := HKLM
 begin
  if IsWin64 then
  begin
   regRoot := HKLM64
  end;
 end;
 if (RegGetSubkeyNames(regRoot, 'SOFTWARE\JavaSoft\Java Runtime Environment', Versions)) or (RegGetSubkeyNames(regRoot, 'SOFTWARE\JavaSoft\Java Development Kit', Versions)) then
 begin
  for I := 0 to GetArrayLength(Versions)-1 do
   if JavaInstalled = true then
   begin
    //do nothing
   end else
   begin
    if ( Versions[I][2]='.' ) and ( ( StrToInt(Versions[I][1]) > 1 ) or ( ( StrToInt(Versions[I][1]) = 1 ) and ( StrToInt(Versions[I][3]) >= 7 ) ) ) then
    begin
     JavaInstalled := true;
    end else
    begin
     JavaInstalled := false;
    end;
   end;
 end else
 begin
  JavaInstalled := false;
 end;

 if JavaInstalled then
 begin
  Result := true;
 end else
    begin
  ResultMsg := MsgBox('Oracle Java v1.7 or newer not found in the system. Java 1.7 or later is required to run this application (can be installed after this installation too). Do you want to continue?',
   mbConfirmation, MB_YESNO) = idYes;
  if ResultMsg = false then
  begin
   Result := false;
  end else
  begin
   Result := true;
   ShellExec('open',
    'http://www.java.com/getjava/',
    '','',SW_SHOWNORMAL,ewNoWait,ErrorCode);
  end;
    end;
end;

end.