怎么自定义 enum类型
如何自定义 enum类型
package com.jin.enums; 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), PLUTO (1.27e+22, 1.137e6); private final double mass; // in kilograms private final double radius; // in meters Planet(double mass, double radius) { this.mass = mass; this.radius = radius; } public double mass() { return mass; } public double radius() { return radius; } // universal gravitational constant (m3 kg-1 s-2) public static final double G = 6.67300E-11; public double surfaceGravity() { return G * mass / (radius * radius); } public double surfaceWeight(double otherMass) { return otherMass * surfaceGravity(); } }
形式二
package com.jin.enums; public enum Operation { // PLUS, MINUS, TIMES, DIVIDE; // // // Do arithmetic op represented by this constant // double eval(double x, double y){ // switch(this) { // case PLUS: // { // System.out.println("aa"); // System.out.println("aa"); // System.out.println("aa"); // return x + y; // } // case MINUS: return x - y; // case TIMES: return x * y; // case DIVIDE: return x / y; // } // throw new AssertionError("Unknown op: " + this); // } PLUS { double eval(double x, double y) { return x + y; } }, MINUS { double eval(double x, double y) { return x - y; } }, TIMES { double eval(double x, double y) { return x * y; } }, DIVIDE { double eval(double x, double y) { return x / y; } }; // Do arithmetic op represented by this constant abstract double eval(double x, double y); }
形式三:
package com.jin.enums; public enum Color { RED, GREEN, YELLOW, BLUCK }
使用:
package com.jin.enums; public class Test { public static void main(String[] args) { // System.out.println(Color.valueOf("RED")); // System.out.println(Planet.VENUS.radius()); System.out.println(Operation.PLUS.eval(1, 3)); } }