Java中hashCode和equals方法的正确使用

　　使用Apache Commons Lang包重写hashCode() 和equals()方法

　　Apache Commons 包提供了两个非常的类来生成hashCode()和equals()方法。看下面的程序。

    import org.apache.commons.lang3.builder.EqualsBuilder; 
    import org.apache.commons.lang3.builder.HashCodeBuilder; 
    public class Employee 
    { 
     private Integer id; 
     private String firstname; 
     private String lastName; 
     private String department; 
    public Integer getId() { 
        return id; 
     } 
     public void setId(Integer id) { 
        this.id = id; 
     } 
     public String getFirstname() { 
        return firstname; 
     } 
     public void setFirstname(String firstname) { 
        this.firstname = firstname; 
     } 
     public String getLastName() { 
        return lastName; 
     } 
     public void setLastName(String lastName) { 
        this.lastName = lastName; 
     } 
     public String getDepartment() { 
        return department; 
     } 
     public void setDepartment(String department) { 
        this.department = department; 
     } 
    @Override
     public int hashCode() 
     { 
        final int PRIME = 31; 
        return new HashCodeBuilder(getId()%2==0?getId()+1:getId()， PRIME). 
               toHashCode(); 
     } 
    @Override
     public boolean equals(Object o) { 
        if (o == null) 
           return false; 
        if (o == this) 
           return true; 
        if (o.getClass() != getClass()) 
           return false; 
        Employee e = (Employee) o; 
           return new EqualsBuilder(). 
                  append(getId()， e.getId()). 
                  isEquals(); 
        } 
     }