Lang-其它好用的 Utils

lang.time 底下好用的 Utils (org.apache.commons.lang.time)

    // 將日期轉為字串
    Date date1 = new Date();
    String formatDate = DateFormatUtils.format(date1, "yyyy-MM-dd");
    System.out.println(formatDate);
        
    // 將字串轉為日期
    Date date2 = DateUtils.parseDate(formatDate, new String[] {"yyyyMMdd", "yyyy-MM-dd" });
    System.out.println(date2);
        
    // 只有比較日期, 沒有比較時間, 所以會回傳 true
    boolean isSameDay = DateUtils.isSameDay(date1, date2);
    System.out.println(isSameDay);

lang.builder 底下好用的 Utils (org.apache.commons.lang.builder)
#) EqualsBuilder 要 override equals 時,

public boolean equals(Object obj) {
   if (obj == null) { return false; }
   if (obj == this) { return true; }
   if (obj.getClass() != getClass()) {
     return false;
   }
   MyClass rhs = (MyClass) obj;
   return new EqualsBuilder()
                 .appendSuper(super.equals(obj))
                 .append(field1, rhs.field1)
                 .append(field2, rhs.field2)
                 .append(field3, rhs.field3)
                 .isEquals();
}
// or 
public boolean equals(Object obj) {
   return EqualsBuilder.reflectionEquals(this, obj);
}

#) HashCodeBuilder 要 override hashCode 時,

 public class Person {
   String name;
   int age;
   boolean smoker;
   ...

   public int hashCode() {
     // you pick a hard-coded, randomly chosen, non-zero, odd number
     // ideally different for each class
     return new HashCodeBuilder(17, 37).
       append(name).
       append(age).
       append(smoker).
       toHashCode();
   }
}
// or 
public int hashCode() {
   return HashCodeBuilder.reflectionHashCode(this);
}

#) ToStringBuilder 要看物件裡有什麼內容時,
1. override toString()

 public class Person {
   String name;
   int age;
   boolean smoker;
 
   ...
 
   public String toString() {
     return new ToStringBuilder(this).
       append("name", name).
       append("age", age).
       append("smoker", smoker).
       toString();
   }
}

2. 直接將 Object 印出來

Person P = new Person();
p.setName("hank");
...
ToStringBuilder.reflectionToString(p);
// or 
ToStringBuilder.reflectionToString(ToStringStyle.MULTI_LINE_STYLE, p);