转载须注明出自：，

货币，Cointrader中基本实体。我们通过代码来学习该实体：

package org.cryptocoinpartners.schema;import java.util.List;import javax.persistence.Cacheable;import javax.persistence.Entity;import javax.persistence.NoResultException;import org.cryptocoinpartners.util.PersistUtil;/** * @author Tim Olson */@Entity //实体@Cacheablepublic class Currency extends Asset {//货币是资产的一种，继承关系    public boolean isFiat() {//是否为法定货币        return fiat;    }    public static Currency forSymbol(String symbol) {        return PersistUtil.queryOne(Currency.class, "select c from Currency c where symbol=?1", symbol);    }    public static List
    
      allSymbols() {        return PersistUtil.queryList(String.class, "select symbol from Currency");    }    // JPA    protected Currency() {    }    protected void setFiat(boolean fiat) {        this.fiat = fiat;    }    // used by Currencies    static Currency forSymbolOrCreate(String symbol, boolean isFiat, double basis) {        try {            return forSymbol(symbol);        } catch (NoResultException e) {            final Currency currency = new Currency(isFiat, symbol, basis);            PersistUtil.insert(currency);            return currency;        }    }    // used by Currencies    static Currency forSymbolOrCreate(String symbol, boolean isFiat, double basis, double multiplier) {        try {            return forSymbol(symbol);        } catch (NoResultException e) {            final Currency currency = new Currency(isFiat, symbol, basis, multiplier);            PersistUtil.insert(currency);            return currency;        }    }    private Currency(boolean fiat, String symbol, double basis) {        super(symbol, basis);        this.fiat = fiat;    }    private Currency(boolean fiat, String symbol, double basis, double multiplier) {        super(symbol, basis);        this.fiat = fiat;        this.multiplier = multiplier;    }    private boolean fiat;//是否为法定货币    private double multiplier;//乘数}
    

还是一个比较难的概念。