1. 입력받기

public static void main(String[] args) throws Exception{
	System.setIn(new FileInputStream("src/main/java/input.txt"));
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	//한 줄 입력
	StringTokenizer st = new StringTokenizer(br.readline);
	N = Integer.parseInt(st.nexttoken());
	//띄어쓰기 입력
	st = new StringTokenizer(br.readline);
	for(int n=0;n<N;n++){
		arr[n] = st.nextToken();
	}
}

2. StringBuilder

StringBuilder sb = new StringBuilder();
sb.append("!@#!@"); //이어붙이기

String str = sb.toStirng(); //String으로!

참고자료

점프 투 파이썬