Java枚举类的规范设计与常见错误规避指南

public enum Color {
    RED, GREEN, BLUE;
}

enum Status {
    PC-TWA; // 编译错误：标识符中不能包含连字符
}

enum Status {
    PC_TWA; // 合法命名
}

enum Status {
    SUCCESS(200), FAILED(500);
    int code;

    Status(int code) {
        this.code = code;
    }

    void setCode(int code) { // 错误：枚举字段不应提供setter
        this.code = code;
    }
}

enum Status {
    SUCCESS(200), FAILED(500);
    private final int code;

    Status(int code) {
        this.code = code;
    }

    public int getCode() {
        return code;
    }
}

Color c1 = Color.RED;
String colorName = "RED";
if (c1 == colorName) { // 编译错误：类型不匹配
    System.out.println("Equal");
}

Color c1 = Color.RED;
if (c1 == Color.RED) {
    System.out.println("Equal via == ");
}
if (c1.equals(Color.RED)) {
    System.out.println("Equal via equals()");
}

enum Status {
    @Deprecated
    OLD_STATUS(1),
    NEW_STATUS(2);
    private final int code;

    Status(int code) {
        this.code = code;
    }

    public static Status fromCode(int code) {
        for (Status status : values()) {
            if (status.code == code) {
                return status;
            }
        }
        throw new IllegalArgumentException("Invalid code: " + code);
    }
}

enum Operation {
    ADD {
        @Override
        public int apply(int a, int b) {
            return a + b;
        }
    },
    SUB {
        @Override
        public int apply(int a, int b) {
            return a - b;
        }
    };

    public abstract int apply(int a, int b);
}

enum DiscountStrategy {
    NONE {
        @Override
        public double apply(double price) {
            return price;
        }
    },
    TEN_PERCENT {
        @Override
        public double apply(double price) {
            return price * 0.9;
        }
    };

    public abstract double apply(double price);
}

enum Status {
    SUCCESS("success"), FAILED("failed");

    private final String description;

    Status(String description) {
        this.description = description;
    }

    public String getLocalizedMessage(Locale locale) {
        return ResourceBundle.getBundle("messages", locale)
                .getString(name().toLowerCase());
    }
}

enum Status {
    SUCCESS, FAILED, PENDING; // 新增PENDING
}

void handleStatus(Status status) {
    switch (status) {
        case SUCCESS:
            // ...
            break;
        case FAILED:
            // ...
            break;
        default: // 可能匹配PENDING，需显式处理
            throw new IllegalArgumentException("Unknown status: " + status);
    }
}