java中的枚举-导致编译时错误的变量声明序列
我创建了enum,如下所示:java中的枚举-导致编译时错误的变量声明序列,java,enums,Java,Enums,我创建了enum,如下所示: public enum Planet { MERCURY(3.303e+23, 2.4397e6), VENUS(4.869e+24, 6.0518e6), EARTH(5.976e+24, 6.37814e6), MARS(6.421e+23, 3.3972e6), JUPITER(1.9e+27, 7.1492e7), SATURN( 5.688e+26, 6.0268e7), URANUS(8.686e+
public enum Planet {
MERCURY(3.303e+23, 2.4397e6), VENUS(4.869e+24, 6.0518e6), EARTH(5.976e+24,
6.37814e6), MARS(6.421e+23, 3.3972e6), JUPITER(1.9e+27, 7.1492e7), SATURN(
5.688e+26, 6.0268e7), URANUS(8.686e+25, 2.5559e7), NEPTUNE(
1.024e+26, 2.4746e7);
private final double mass; // in kilograms
private final double radius; // in meters
Planet(double mass, double radius) {
this.mass = mass;
this.radius = radius;
}
但若我将变量声明为enum中的第一条语句,编译器将不会像这样接受它
public enum Planet {
private final double mass; // in kilograms
private final double radius; // in meters
MERCURY(3.303e+23, 2.4397e6), VENUS(4.869e+24, 6.0518e6), EARTH(5.976e+24,
6.37814e6), MARS(6.421e+23, 3.3972e6), JUPITER(1.9e+27, 7.1492e7), SATURN(
5.688e+26, 6.0268e7), URANUS(8.686e+25, 2.5559e7), NEPTUNE(
1.024e+26, 2.4746e7);
Planet(double mass, double radius) {
this.mass = mass;
this.radius = radius;
}
知道为什么吗??理解可能这就是enum规范所说的,但我试图从编译器的角度理解变量声明序列如何困扰编译器???创建enum时,枚举值应始终是第一个声明的值。这正是枚举的java语法的定义方式-枚举值是您首先要写的内容,然后才是实例字段和方法等 请参阅本手册的相关部分: 理解可能这就是enum规范所说的,但我试图从编译器的角度理解变量声明序列是如何困扰编译器的 没有任何答案可以完全忽略该规范。基本上,该规范不提供编译器应将哪些语句解释为枚举值的标志。语言规范只允许使用第一条语句作为指示符
EnumDeclaration:
ClassModifiersopt enum Identifier Interfacesopt EnumBody
EnumBody:
{ EnumConstantsopt ,opt EnumBodyDeclarationsopt }
EnumConstants:
EnumConstant
EnumConstants , EnumConstant