//声明 new String().var
String s = new String();
//判空 方式1: 变量声明后,ifn; 方式2: s.null
if (s == null) {
}
//判非空 方式1: s.notnull; 方式2: s.nn
if (s != null) {
}
//遍历 list.for
ArrayList<Object> list = new ArrayList<>();
for (Object o : list) {
}
//带索引遍历 从小到大: list.fori; 从大到小: list.forr
for (int i = 0; i < list.size(); i++) {
}
for (int i = list.size() - 1; i >= 0; i--) {
}
//取反 success.not
Boolean success = true;
//success.not --> !success
//条件判断 if success.if
if (success) {
}
//强转 cast 方式1: name.cast --> (String)name; 方式2: name.castvar --> String name2 = (String) name;
Object name = "xz";
String name1 = (String) name;
String name2 = (String) name;
//返回 return name.return --> return name;
//return name;
