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How to Juice your Java Performance

· Performance Zone

See Gartner’s latest research on the application performance monitoring landscape and how APM suites are becoming more and more critical to the business, brought to you in partnership with AppDynamics.

In my previous post about equals and hashcode I thought I'd point out how to redesign the class in question to make better use of performance. If you have a situation where you create groups of objects that are immutable, but you need to pass them around in hashsets and/or look things up, a way to increase performance is to change from something like the following:

package blog.mainguy;

import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;

public class LookupEntity {
    private String name;

    public void setName(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    @Override
    public boolean equals(Object other) {
        if (other != null && other instanceof LookupEntity) {
            return new EqualsBuilder().append(this.getName(), ((LookupEntity) other).getName()).isEquals();
        } else {
            return false;
        }
    }

    @Override
    public int hashCode() {
        return new HashCodeBuilder(17,31).append(this.getName()).hashCode();
    }
}


to something like

package blog.mainguy;

import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;

public class LookupEntity {
    private String name;
    private LookupEntity() {
    }
    public LookupEntity(String name) {
        
        this.name = name == null?"":name;
        hashCode = name.hashCode();
    }
    public String getName() {
        return name;
    }
    private int hashCode;

    @Override
    public boolean equals(Object other) {
       if (other != null && other instanceof LookupEntity) {
            return this.name.equals(((LookupEntity)other).getName())
        }
    }

    @Override
    public int hashCode() {
        return hashCode;
    }
}

Note, I have not profiled this, it is based on my perception and understanding of how java works. It is also (as I noted) a pre-optimization that I personally wouldn't necessarily start with (though in many cases I might).

The Performance Zone is brought to you in partnership with AppDynamics.  See Gartner’s latest research on the application performance monitoring landscape and how APM suites are becoming more and more critical to the business.

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Published at DZone with permission of Michael Mainguy , DZone MVB .

Opinions expressed by DZone contributors are their own.

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