Java Tutorial/Apache Common/HashCodeBuilder
Содержание
Custom HashCode Builder
<source lang="java">
/*
* ======================================================================== * * Copyright 2005 Tim O"Brien. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * * ======================================================================== */
import java.math.BigDecimal; import java.util.HashSet; import java.util.Set; import org.apache.rumons.lang.builder.rupareToBuilder; import org.apache.rumons.lang.builder.EqualsBuilder; import org.apache.rumons.lang.builder.HashCodeBuilder; import org.apache.rumons.lang.builder.ToStringBuilder; class TaxReturn {
private String ssn;
private int year;
private String lastName;
private BigDecimal taxableIncome;
public TaxReturn() {
}
public TaxReturn(String pSsn, int pYear, String pLastName, BigDecimal pTaxableIncome) {
setSsn(pSsn);
setYear(pYear);
setLastName(pLastName);
setTaxableIncome(pTaxableIncome);
}
public String getSsn() {
return ssn;
}
public void setSsn(String pSsn) {
ssn = pSsn;
}
public int getYear() {
return year;
}
public void setYear(int pYear) {
year = pYear;
}
public String getLastName() {
return lastName;
}
public void setLastName(String pLastName) {
lastName = pLastName;
}
public BigDecimal getTaxableIncome() {
return taxableIncome;
}
public void setTaxableIncome(BigDecimal pTaxableIncome) {
taxableIncome = pTaxableIncome;
}
public String toString() {
return new ToStringBuilder(this).append("ssn", ssn).append("year", year).append("lastName",
lastName).toString();
}
public int hashCode() {
return new HashCodeBuilder(3, 7).append(ssn).append(year).toHashCode();
}
public boolean equals(Object pObject) {
boolean equals = false;
if (pObject instanceof TaxReturn) {
TaxReturn bean = (TaxReturn) pObject;
equals = (new EqualsBuilder().append(ssn, bean.ssn).append(year, bean.year)).isEquals();
}
return equals;
}
public int compareTo(Object pObject) {
return CompareToBuilder.reflectionCompare(this, pObject);
}
} public class MainClass {
public static void main(String[] pArgs) throws Exception {
TaxReturn return1 = new TaxReturn("012-68-3242", 1998, "O"Brien", new BigDecimal(43000.00));
TaxReturn return2 = new TaxReturn("012-68-3242", 1999, "O"Brien", new BigDecimal(45000.00));
TaxReturn return3 = new TaxReturn("012-68-3242", 1999, "O"Brien", new BigDecimal(53222.00));
System.out.println("HashCodeBuilder: " + return2.hashCode());
Set set = new HashSet();
set.add(return1);
set.add(return2);
set.add(return3);
System.out.println(set);
}
}</source>
HashCodeBuilder: 219210998 [TaxReturn@7ffe01[ssn=012-68-3242,year=1998,lastName=O"Brien], TaxReturn@471e30[ssn=012-68-3242,year=1999,lastName=O"Brien]]
HashCode Builder
<source lang="java">
/*
* ======================================================================== * * Copyright 2005 Tim O"Brien. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * * ======================================================================== */
import org.apache.rumons.lang.builder.rupareToBuilder; import org.apache.rumons.lang.builder.EqualsBuilder; import org.apache.rumons.lang.builder.HashCodeBuilder; import org.apache.rumons.lang.builder.ReflectionToStringBuilder; class BuilderBean implements Comparable {
private String prop1;
private String prop2;
public String getProp1() {
return prop1;
}
public void setProp1(String pProp1) {
prop1 = pProp1;
}
public String getProp2() {
return prop2;
}
public void setProp2(String pProp2) {
prop2 = pProp2;
}
public String toString() {
return ReflectionToStringBuilder.toString(this);
}
public boolean equals(Object pObject) {
return EqualsBuilder.reflectionEquals(this, pObject);
}
public int compareTo(Object pObject) {
return CompareToBuilder.reflectionCompare(this, pObject);
}
public int hashCode() {
return HashCodeBuilder.reflectionHashCode(this);
}
} public class MainClass {
public static void main(String[] pArgs) throws Exception {
// Builder and Builder2 contain the same content
BuilderBean builder = new BuilderBean();
builder.setProp1("One");
builder.setProp2("Two");
BuilderBean builder2 = new BuilderBean();
builder2.setProp1("One");
builder2.setProp2("Two");
BuilderBean builder3 = new BuilderBean();
builder3.setProp1("Uno");
builder3.setProp2("Dos");
System.out.println("HashCodeBuilder: " + builder.hashCode());
}
}</source>
HashCodeBuilder: 3046707
HashCodeBuilder.reflectionHashCode
<source lang="java">
import org.apache.rumons.lang.builder.EqualsBuilder; import org.apache.rumons.lang.builder.HashCodeBuilder; import org.apache.rumons.lang.builder.ToStringBuilder; import org.apache.rumons.lang.builder.ToStringStyle; public class MainClass {
public static void main(String[] args) {
MyClass one = new MyClass("Becker", 35);
MyClass two = new MyClass("Becker", 35);
MyClass three = new MyClass("Agassi", 33);
System.out.println("One>>>" + one);
System.out.println("Two>>>" + two);
System.out.println("Three>>>" + three);
System.out.println("one equals two? " + one.equals(two));
System.out.println("one equals three? " + one.equals(three));
System.out.println("One HashCode>>> " + one.hashCode());
System.out.println("Two HashCode>>> " + two.hashCode());
System.out.println("Three HashCode>>> " + three.hashCode());
}
} class MyClass {
private String name = null;
private int age = 0;
public MyClass(String name, int age) {
this.name = name;
this.age = age;
}
public boolean equals(Object obj) {
return EqualsBuilder.reflectionEquals(this, obj);
}
public String toString() {
return ToStringBuilder.reflectionToString(this,
ToStringStyle.MULTI_LINE_STYLE);
}
public int hashCode() {
return HashCodeBuilder.reflectionHashCode(this);
}
}</source>
One>>>MyClass@743399[ name=Becker age=35 ] Two>>>MyClass@1d8957f[ name=Becker age=35 ] Three>>>MyClass@3ee284[ name=Agassi age=33 ] one equals two? true one equals three? false One HashCode>>> 462213092 Two HashCode>>> 462213092 Three HashCode>>> -530629296
HashCode For String
<source lang="java">
import org.apache.rumons.lang.builder.EqualsBuilder; import org.apache.rumons.lang.builder.HashCodeBuilder; import org.apache.rumons.lang.builder.ToStringBuilder; import org.apache.rumons.lang.builder.ToStringStyle;
public class MainClass {
public static void main(String[] args) {
//Create new BuilderTrial instances
BuilderTrial one = new BuilderTrial("Becker", 35);
BuilderTrial two = new BuilderTrial("Becker", 35);
BuilderTrial three = new BuilderTrial("Agassi", 33);
//one and two hold the same data in different objects
//three holds different data
System.out.println("One>>>" + one);
System.out.println("Two>>>" + two);
System.out.println("Three>>>" + three);
System.out.println("one equals two? " + one.equals(two));
System.out.println("one equals three? " + one.equals(three));
//As one and two hold the same data, the same hashcode is returned.
System.out.println("One HashCode>>> " + one.hashCode());
System.out.println("Two HashCode>>> " + two.hashCode());
System.out.println("Three HashCode>>> " + three.hashCode());
}
} class BuilderTrial {
private String name;
private int age;
public BuilderTrial(String name, int age) {
this.name = name;
this.age = age;
}
public static void main(String[] args) {
}
public boolean equals(Object objCompared) {
if (!(objCompared instanceof BuilderTrial)) {
return false;
}
BuilderTrial rhs = (BuilderTrial) objCompared;
return new EqualsBuilder().append(name, rhs.name).append(age, rhs.age)
.isEquals();
}
public String toString() {
return new ToStringBuilder(this, ToStringStyle.MULTI_LINE_STYLE).append("Name",
name).append("Age", age).toString();
}
public int hashCode() {
return new HashCodeBuilder(15, 19).append(name).append(age).toHashCode();
}
}</source>
One>>>BuilderTrial@a981ca[ Name=Becker Age=35 ] Two>>>BuilderTrial@e7b241[ Name=Becker Age=35 ] Three>>>BuilderTrial@167d940[ Name=Agassi Age=33 ] one equals two? true one equals three? false One HashCode>>> -923455822 Two HashCode>>> -923455822 Three HashCode>>> -1433293806
