☕️ void run() { int count; count++; // IDE 报错,Variable 'count' might not have been initialized } 既然这样,那我们就给它一个默认值 null 吧,遗憾的是你会发现仍然报错。 ️ class Sample { var v: View = null // 这样写 IDE 仍然会报错,Null can not be a value of a non-null...
filter only the ones that are CSV files and read the contents of each file. Once we have the lines of each CSV files we separate the first line, that contains the header, from the rest of the content. Then we get the names of the columns from the header line. ...
savedInstanceState.getBoolean("locked"); } 在Java 中,这段代码将编译正常,访问 null 对象将导致应用在运行时崩溃并抛出NullPointerException。现在让我们来看看相同方法的 Kotlin 版本: override fun onCreate(savedInstanceState: Bundle?) { //1 super.onCreate(savedInstanceState) savedInstanceState.getBoolean(...
Kotlin is smart enough to understand that"John"is aString(text), and that1975is anInt(number) variable. However, it is possible to specify the type if you insist: Example varname:String="John"// Stringvalbirthyear:Int=1975// Intprintln(name)println(birthyear) ...
Here, language is a variable of type String, and score is a variable of type Int. You don't have to specify the type of variables; Kotlin implicitly does that for you. The compiler knows this by initializer expression ("French" is a String, and 95 is an integer value in the above ...
publicstatictestGenerics()Ljava/lang/Object;L0LINENUMBER13L0ACONST_NULLASTORE0L1LINENUMBER14L1ALOAD0ARETURNL2LOCALVARIABLEt Ljava/lang/Object;L1L20// signature TT;// declaration: TMAXSTACK=1MAXLOCALS=1 我们看到,编译之后 T 变成了 Object,简单来说就相当于: ...
DUP IFNULL L1 //对Char判空 INVOKEVIRTUAL java/lang/Object.hashCode ()I INVOKESTATIC java/lang/Integer.valueOf (I)Ljava/lang/Integer; GOTO L2 L1 POP ACONST_NULL L2 INVOKEVIRTUAL java/io/PrintStream.println (Ljava/lang/Object;)V L3 LINENUMBER 12 L3 RETURN L4 LOCALVARIABLE string Ljava/lang...
public enum class AnnotationTarget { CLASS, //表示作用对象有类、接口、object对象表达式、注解类 ANNOTATION_CLASS,//表示作用对象只有注解类 TYPE_PARAMETER,//表示作用对象是泛型类型参数(暂时还不支持) PROPERTY,//表示作用对象是属性 FIELD,//表示作用对象是字段,包括属性的幕后字段 LOCAL_VARIABLE,//表示作用...
//代表被注解的元素 variableElemet是element的子类 VariableElement variableElement = (VariableElement) element; //被注解元素所在的class TypeElement typeElement = (TypeElement) variableElement.getEnclosingElement(); //class的完整路径 String classFullName = typeElement.getQualifiedName().toString(); ...
KProperty is obtainable using the :: operator and has a name property that lets us get the property’s name. We’ll use this below to get the name of a class’s property: class MyClass(val age: Int, var name: String, val next: MyClass?) Assertions.assertEquals("next", MyClass::...