override the equals & hashcode & compareTo & toString

总结一下相关的 equals/ hashCode / compareTo / toString method写法
1. org.apache.commons.lang.builder.EqualsBuilder
注意：复写equals,必须要复写hashCode, 在equals比较的Field必须也出现在hashCode里，反之亦然。
@Override
public boolean equals(Object o) {
if (o == null) { return false; }
if (! (o instanceof AccountInstrument)) {
return false;
}
if (o == this) { return true; }
AccountInstrument rhs = (AccountInstrument) o;
return new EqualsBuilder()
.append(accountId, rhs.accountId)
.append(instrumentId, rhs.instrumentId)
.isEquals();

}
2. org.apache.commons.lang.builder.HashCodeBuilder
请参考equals, 可以使用HashCodeBuilder(17, 35) as HashCodeBuilder(int initialNonZeroOddNumber, int multiplierNonZeroOddNumber)选择任意、非零、奇数
// cache for toString() and hashCode() as this is a immutable object
private Integer hashCodeCache = null;
private String toStringCache = null;
@Override
public int hashCode() {
if (hashCodeCache == null) {
hashCodeCache = new HashCodeBuilder()
.append(accountId).append(instrumentId).toHashCode();
}
return hashCodeCache;
}

3. org.apache.commons.lang.builder.ToStringBuilder
ToStringStyle定义输出的格式，可以创建子类实现新的输出格式。
@Override
public String toString() {
if (toStringCache == null) {
toStringCache = ToStringBuilder.reflectionToString(this, ToStringStyle.DEFAULT_STYLE);
}
return toStringCache;
}
在API文档的例子：
public class MyStyle extends ToStringStyle {
protected void appendDetail(StringBuffer buffer, String fieldName, Object value) {
if (value instanceof Date) {
value = new SimpleDateFormat("yyyy-MM-dd").format(value);
}
buffer.append(value);
}
}


4. org.apache.commons.lang.builder.CompareToBuilder
public int compareTo(AccountInstrument o) {
return new CompareToBuilder()
.append(this.accountId, o.accountId)
.append(this.instrumentId, o.instrumentId)
.toComparison();
}