Fastest input in Java

Hi guys I’m trying to solve Java Practice problems here. I’ve noticed that instead of using the Scanner object and taking inputs if I create a suppose readInt() func and take input the Runtime is way faster.

For instance here is my readInt() which I use to take integer inputs just like a Scanner does.

  static int readInt() throws IOException{
	int number = 0;
	int neg = 1;
	if(offset==bufferSize){
		offset = 0;
		bufferSize = in.read(buffer);
	}
	for(;buffer[offset]<0x30 || buffer[offset]=='-'; ++offset)
	{
		if (buffer[offset]=='-')
			neg = -1;
		if(offset==bufferSize-1){
			offset=-1;
			bufferSize = in.read(buffer);
		}
	}
	for(;offset<bufferSize && buffer[offset]>0x2f;++offset){
		number = number*0x0a+buffer[offset]-0x30;
		if(offset==bufferSize-1){
			offset = -1;
			bufferSize = in.read(buffer);
		}
	}
	++offset;
	return number*neg;
} 

Is there any similar mehtod for Double and String variables. Scanner seems to take a lot of execution time. Also why does the scanner take so much time??

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