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);
}