gistfile1.txt

package com.example;

import android.support.annotation.IntDef;
import android.util.SparseArray;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

import static com.example.Size.ValidSize.SIZE_L;
import static com.example.Size.ValidSize.SIZE_M;
import static com.example.Size.ValidSize.SIZE_S;


public enum Size {
    L(SIZE_L), M(SIZE_M), S(SIZE_S);

    private volatile static SparseArray<Size> rawValueToEnum;

    @ValidSize
    private final int rawValue;

    Size(@ValidSize int rawValue) {
        this.rawValue = rawValue;
    }

    @ValidSize
    public int getRawValue() {
        return rawValue;
    }

    @Retention(RetentionPolicy.SOURCE)
    @IntDef({SIZE_L, SIZE_M, SIZE_S})
    public @interface ValidSize {
        int SIZE_L = 1;
        int SIZE_M = 2;
        int SIZE_S = 3;
    }

    public static Size fromRawValue(int rawValue) {
        if (rawValueToEnum == null) {
            final SparseArray<Size> sizeSparseArray = new SparseArray<>();
            final Size[] values = values();
            for (Size size : values) {
                sizeSparseArray.append(size.getRawValue(), size);
            }

            // おまけ。値の重複チェックをしておく
            if (sizeSparseArray.size() != values.length) {
                throw new IllegalStateException("duplicate rawValues in Size enum");
            }

            rawValueToEnum = sizeSparseArray;
        }

        final Size size = rawValueToEnum.get(rawValue);
        if (size == null) {
            throw new IllegalArgumentException("invalid rawValue: " + rawValue);
        }
        return size;
    }
}