1.列表拼接成字符串
#1.1
String result = Joiner.on("_").join(list);
#1.2
String result = list.stream().collect(Collectors.joining("_"));
2.Java8的foreach()中使用return/break/continue
foreach()处理集合时不能使用break和continue这两个方法
可以试用return实现continue的功能(return不会退出循环)
举例
public static void main(String[] args) {
List<String> lst = Arrays.asList("12", "3", "12345", "123");
lst.stream().forEach(e->{
if (e.length() >= 5){
return;
}
System.out.println(e);
});
}
输出
12
3
123
3. 计算耗时
StopWatch stopWatch = new StopWatch();
stopWatch.start("testStopWatch");
stopWatch.stop();
double thickestWorkSeconds = stopWatch.getTotalTimeSeconds();
4.切割 split
List<String> mm = Arrays.asList("1243+122".split("+"));
提示报错:Dangling quantifier '+'
解:需转义:"1243+122".split("\\+")