没废话之Java字符串常用用法

String s = "abcde";

String s = s1 + s2;

String s1 = s.substring(0,3)                           //区间前闭后开

String s = String.join(",", "a", "b", "c");               //输出为a,b,c

Boolean bool = s1.eauals(s2);

int len = s.length();

Boolean bool = s.length == 0;
Boolean bool = s.equals("");

char cha = s.charAt(i);

String s1 = s.toLowerCase;
String s2 = s.toUpperCase;

String s1 = s.trim();