Read Assets file as string

getAssets().open() will return an InputStream. Read from that using standard Java I/O:

Java:

StringBuilder sb = new StringBuilder();
InputStream is = getAssets().open("book/contents.json");
BufferedReader br = new BufferedReader(new InputStreamReader(is, StandardCharsets.UTF_8 ));
String str;
while ((str = br.readLine()) != null) {
    sb.append(str);
}
br.close();

Kotlin:

val str = assets.open("book/contents.json").bufferedReader().use { it.readText() }

There is a little bug CommonsWare's code - newline characters are discarded and not added to the string. Here is some fixed code ready for copy+paste:

private String loadAssetTextAsString(Context context, String name) {
        BufferedReader in = null;
        try {
            StringBuilder buf = new StringBuilder();
            InputStream is = context.getAssets().open(name);
            in = new BufferedReader(new InputStreamReader(is));

            String str;
            boolean isFirst = true;
            while ( (str = in.readLine()) != null ) {
                if (isFirst)
                    isFirst = false;
                else
                    buf.append('\n');
                buf.append(str);
            }
            return buf.toString();
        } catch (IOException e) {
            Log.e(TAG, "Error opening asset " + name);
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    Log.e(TAG, "Error closing asset " + name);
                }
            }
        }

        return null;
    }