import org.apache.commons.lang.builder.HashCodeBuilder;
import org.apache.commons.lang.builder.EqualsBuilder;
public class PoliticalCandidate {
// Member variables - omitted for brevity
// Constructors - omitted for brevity
// get/set methods - omitted for brevity
// A hashCode which creates a hash from the two unique identifiers
public int hashCode( ) {
return new HashCodeBuilder( 17 , 37 )
.append(firstName)
.append(lastName).toHashCode( );
}
// An equals which compares two unique identifiers
public boolean equals(Object o) {
boolean equals = false ;
if ( o != null && PoliticalCandidate. class .isAssignableFrom(o) ) {
PoliticalCandidate pc = (PoliticalCandidate) o;
equals = ( new EqualsBuilder( )
.append(firstName, ps.firstName)
.append(lastName, ps.lastName)).isEquals( );
}
return equals;
}
}
public int hashCode( ) {
return HashCodeBuilder.reflectionHashCode( this );
} public boolean equals(Object o) {
return EqualsBuilder.reflectionEquals( this , o);
} 問題提出：需要快速實現compareTo()方法 解決方法：使用CompareToBuilder提供的compareTo()方法。同樣的CompareToBuilder也使用了反射機制。以下代碼提供了一個compareTo()方法，用於比較兩個對象所有的非static和非transient成員變量。
import org.apache.commons.lang.builder.CompareToBuilder;
// Build a compareTo function from reflection
public int compareTo(Object o) {
return CompareToBuilder.reflectionCompare( this , obj);
} public class PoliticalCandidate {
// Static variable
private static String averageAge;
// Member variables
private String firstName;
private String lastName;
private transient String fullName;
// Constructors
// get/set methods
// Build a compareTo function from reflection
public int compareTo(Object o) {
return CompareToBuilder.reflectionCompare( this , obj);
}
} public int compareTo(Object o) {
int compare = - 1 ; // By default return less-than
if ( o != null && PoliticalCandidate. class .isAssignableFrom( o.getClass( ) ) ) {
PoliticalCandidate pc = (PoliticalCandidate) o;
compare = ( new CompareToBuilder( )
.append(firstName, pc.firstName)
.append(lastName, pc.lastName)).toComparison( );
}
return compare;
} 1.1 ReflectionToStringBuilder
本筆記是在閱讀Jakarta Commons Cookbook時所留下的。 1.使用ReflectionToStringBuilder 或者ToStringBuilder 自動產生toString()的內容。 使用舉例：假設有一個表徵校長候選人信息的javabean－PoliticalCandidate。public class PoliticalCandidate {
private String lastName;
private String firstName;
private Date dateOfBirth;
private BigDecimal moneyRaised;
private State homeState;
// get/set方法省略
public void toString( ) {
ReflectionToStringBuilder.toString( this );
}
}// Create a State
State va = new State( "VA", "Virginia");
// Create a Birth Date
Calendar calendar = new GregorianCalendar( );
calendar.set( Calendar.YEAR, 1743 );
calendar.set( Calendar.MONTH, Calendar.APRIL );
calendar.set( Calendar.DAY_OF_MONTH, 13 );
Date dob = calendar.getTime( );
BigDecimal moneyRaised = new BigDecimal( 293829292.93 );
// Create a Political Candidate
PoliticalCandidate candidate =
new PoliticalCandidate( "Jefferson", "Thomas", dob, moneyRaised, va );
System.out.println( candidate );
org.apache.commons.lang.builder
CompareToBuilder – 用於輔助實現Comparable.compareTo(Object)方法；
EqualsBuilder – 用於輔助實現Object.equals()方法；
HashCodeBuilder – 用於輔助實現Object.hashCode()方法；
ToStringBuilder – 用於輔助實現Object.toString()方法；
ReflectionToStringBuilder – 使用反射機制輔助實現Object.toString()方法；
ToStringStyle – 輔助ToStringBuilder控制輸出格式；
StandardToStringStyle – 輔助ToStringBuilder控制標準格式。