java [Java]我想写得更优雅

Posted 2021-05-08

import java.util.HashMap;

public class NumberMap {
    HashMap<String, Number> map = new HashMap<>();

    public void put(String key, Number value) {
        if (value instanceof Double
            || value instanceof Float
            || value instanceof Integer
            || value instanceof Long
            || value instanceof Short) {
            map.put(key, value);
        } else {
            throw new RuntimeException("NumberMap does not support BigDecimal, BigInteger and Byte.");
        }
    }

    public <T extends Number> T get1(String key, T defaultValue) {
        Number ret = map.get(key);
        if (ret == null) {
            return defaultValue;
        } else {
            return (T)ret;
        }
    }

    public <T extends Number> T get2(String key, T defaultValue) {
        Number ret = map.get(key);
        if (ret == null) {
            return defaultValue;
        } else if (defaultValue.getClass().isInstance(ret)) {
            return (T)ret;
        } else if (defaultValue instanceof Double) {
            return (T)((Double)ret.doubleValue());
        } else if (defaultValue instanceof Float) {
            return (T)((Float)ret.floatValue());
        } else if (defaultValue instanceof Integer) {
            return (T)((Integer)ret.intValue());
        } else if (defaultValue instanceof Long) {
            return (T)((Long)ret.longValue());
        } else if (defaultValue instanceof Short) {
            return (T)((Short)ret.shortValue());
        } else {
            throw new RuntimeException("defaultValue must be double|float|int|long|short.");
        }
    }

    public double get3(String key, double defaultValue) {
        Number ret = map.get(key);
        if (ret == null) {
            return defaultValue;
        } else {
            return ret.doubleValue();
        }
    }

    public float get3(String key, float defaultValue) {
        Number ret = map.get(key);
        if (ret == null) {
            return defaultValue;
        } else {
            return ret.floatValue();
        }
    }

    public int get3(String key, int defaultValue) {
        Number ret = map.get(key);
        if (ret == null) {
            return defaultValue;
        } else {
            return ret.intValue();
        }
    }

    public long get3(String key, long defaultValue) {
        Number ret = map.get(key);
        if (ret == null) {
            return defaultValue;
        } else {
            return ret.longValue();
        }
    }

    public short get3(String key, short defaultValue) {
        Number ret = map.get(key);
        if (ret == null) {
            return defaultValue;
        } else {
            return ret.shortValue();
        }
    }

    public static void main(String[] args) {
        NumberMap map = new NumberMap();
        map.put("double", 1.0d);
        map.put("int", 1);

        // NG - java.lang.ClassCastException:
        // java.lang.Integer cannot be cast to java.lang.Double
        double doubleGet1 = map.get1("int", 1.0d);

        // NG - java.lang.ClassCastException:
        // java.lang.Double cannot be cast to java.lang.Integer
        int intGet1 = map.get1("double", 1);

        // OK
        double doubleGet2 = map.get2("int", 1.0d);

        // OK
        int intGet2 = map.get2("double", 1);

        // OK
        double doubleGet3 = map.get3("int", 1.0d);

        // OK
        int intGet3 = map.get3("double", 1);
    }
}