StringBuilder如何大幅减少Java程序所需的时间？

Question

有两个Java代码片段。在下面分享它们-

一,

Collections.sort(al);
                Iterator<Integer> it = al.iterator();
                while(it.hasNext()){
                        sb.append(it.next());
                        sb.append("\n");
                }
                System.out.println(sb.toString());

二,

Collections.sort(al);
                Iterator<Integer> it = al.iterator();
                while(it.hasNext()){
                        System.out.println(it.next());
                }

分享上述计划所花费的时间- 1.1.43秒 2.4.28秒

我想知道magic StringBuilder是做什么的，有人可以指导吗

Answer 1

这不是您的StringBuilder，而是您的系统。出来println（）语句，这会减慢执行时间

它很慢，因为

Bytes had to be sent to the console application -> Each char has to be rendered using a true type font (cause for slow processing) -> Displayed area may have to be scrolled to append a new line to the visible area.