java - Apache Commons equals/hashCode builder -

i'm curious know, people here think using org.apache.commons.lang.builder equalsbuilder/hashcodebuilder implementing equals/hashcode? better practice writing own? play hibernate? what's opinion?

the commons/lang builders great , have been using them years without noticeable performance overhead (with , without hibernate). alain writes, guava way nicer:

here's sample bean:

public class bean{      private string name;     private int length;     private list<bean> children;  } 

here's equals() , hashcode() implemented commons/lang:

@override public int hashcode(){     return new hashcodebuilder()         .append(name)         .append(length)         .append(children)         .tohashcode(); }  @override public boolean equals(final object obj){     if(obj instanceof bean){         final bean other = (bean) obj;         return new equalsbuilder()             .append(name, other.name)             .append(length, other.length)             .append(children, other.children)             .isequals();     } else{         return false;     } } 

and here guava:

@override public int hashcode(){     return objects.hashcode(name, length, children); }  @override public boolean equals(final object obj){     if(obj instanceof bean){         final bean other = (bean) obj;         return objects.equal(name, other.name)             && length == other.length // special handling primitives             && objects.equal(children, other.children);     } else{         return false;     } } 

as can see guava version shorter , avoids superfluous helper objects. in case of equals, allows short-circuiting evaluation if earlier object.equal() call returns false (to fair: commons / lang has objectutils.equals(obj1, obj2) method identical semantics used instead of equalsbuilder allow short-circuiting above).

so: yes, commons lang builders preferable on manually constructed equals() , hashcode() methods (or awful monsters eclipse generate you), guava versions better.

and note hibernate:

be careful using lazy collections in equals(), hashcode() , tostring() implementations. fail miserably if don't have open session.

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note (about equals()):

a) in both versions of equals() above, might want use 1 or both of these shortcuts also:

@override public boolean equals(final object obj){     if(obj == this) return true;  // test reference equality     if(obj == null) return false; // test null     // continue above 

b) depending on interpretation of equals() contract, might change line(s)

    if(obj instanceof bean){ 

to

    // make sure run null check before     if(obj.getclass() == getclass()){  

if use second version, want call super(equals()) inside equals() method. opinions differ here, topic discussed in question:

right way incorporate superclass guava objects.hashcode() implementation?

(although it's hashcode(), same applies equals())

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note (inspired comment kayahr)

objects.hashcode(..) (just underlying arrays.hashcode(...)) might perform badly if have many primitive fields. in such cases, equalsbuilder may better solution.