類基本方法（toString、hashCode、equals、compareTo）重寫

使用jar包為 apache的commons集lang包

1. toString()

實現一

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();
   }
 }

實現二

public String toString() {
   return ToStringBuilder.reflectionToString(this);
 }

2. hashCode()

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();
  }
}

3. equals(Object obj)

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();
 }

4. compareTo(Object o)

public int compareTo(Object o) {
    MyClass myClass = (MyClass) o;
    return new CompareToBuilder()
      .appendSuper(super.compareTo(o)
      .append(this.field1, myClass.field1)
      .append(this.field2, myClass.field2)
      .append(this.field3, myClass.field3)
      .toComparison();
  }