摘要：
这是源程序：```javaString s = ""; for (int i = 0; i < 50000; i ++) { s += i; } StringBuilder sb = new StringBuilder(); for (int i = 0; i < 50000; i ++) { sb.append(i); } StringBuilder sb2 = new StringBuilder(); for (int i = 0; i < 50000; i ++) { sb2.append("s" + i); } String s 阅读全文
