Apache Commons Lang
Implement equals() method
To implement the equals
method of an object easily you could use the EqualsBuilder
class.
Selecting the fields:
@Override
public boolean equals(Object obj) {
if(!(obj instanceof MyClass)) {
return false;
}
MyClass theOther = (MyClass) obj;
EqualsBuilder builder = new EqualsBuilder();
builder.append(field1, theOther.field1);
builder.append(field2, theOther.field2);
builder.append(field3, theOther.field3);
return builder.isEquals();
}
Using reflection:
@Override
public boolean equals(Object obj) {
return EqualsBuilder.reflectionEquals(this, obj, false);
}
the boolean parameter is to indicates if the equals should check transient fields.
Using reflection avoiding some fields:
@Override
public boolean equals(Object obj) {
return EqualsBuilder.reflectionEquals(this, obj, "field1", "field2");
}
Implement hashCode() method
To implement the hashCode
method of an object easily you could use the HashCodeBuilder
class.
Selecting the fields:
@Override
public int hashCode() {
HashCodeBuilder builder = new HashCodeBuilder();
builder.append(field1);
builder.append(field2);
builder.append(field3);
return builder.hashCode();
}
Using reflection:
@Override
public int hashCode() {
return HashCodeBuilder.reflectionHashCode(this, false);
}
the boolean parameter indicates if it should use transient fields.
Using reflection avoiding some fields:
@Override
public int hashCode() {
return HashCodeBuilder.reflectionHashCode(this, "field1", "field2");
}
Implement toString() method
To implement the toString
method of an object easily you could use the ToStringBuilder
class.
Selecting the fields:
@Override
public String toString() {
ToStringBuilder builder = new ToStringBuilder(this);
builder.append(field1);
builder.append(field2);
builder.append(field3);
return builder.toString();
}
Example result:
ar.com.jonat.lang.MyClass@dd7123[<null>,0,false]
Explicitly giving names to the fields:
@Override
public String toString() {
ToStringBuilder builder = new ToStringBuilder(this);
builder.append("field1",field1);
builder.append("field2",field2);
builder.append("field3",field3);
return builder.toString();
}
Example result:
ar.com.jonat.lang.MyClass@dd7404[field1=<null>,field2=0,field3=false]
You could change the style via parameter:
@Override
public String toString() {
ToStringBuilder builder = new ToStringBuilder(this,
ToStringStyle.MULTI_LINE_STYLE);
builder.append("field1", field1);
builder.append("field2", field2);
builder.append("field3", field3);
return builder.toString();
}
Example result:
ar.com.bna.lang.MyClass@ebbf5c[
field1=<null>
field2=0
field3=false
]
There are some styles, for example JSON, no Classname, short, etc …
Via reflection:
@Override
public String toString() {
return ToStringBuilder.reflectionToString(this);
}
You could also indicate the style:
@Override
public String toString() {
return ToStringBuilder.reflectionToString(this, ToStringStyle.JSON_STYLE);
}