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Does the following class satisfy the Java Hash Code contract? Explain. public class Politician{ String firstName; String lastName; /...assume other fields and constructors are implemented public boolean equals(Object obj) { if (obj == this) return true; if (!(obj instanceof Politician)) return false; Politician pol = (Politician)obj; boolean returnVal = (this.firstName+this.lastName).equals(pol.firstName+pol.lastName)); return return Val; } public int hashCode() { return lastName.hashCode(); //last name is a String, so lastName.hashCode() is defined in the String implementatior } }

Does the following class satisfy the Java Hash Code contract? Explain. public class Politician{ String firstName; String lastName; /...assume other fields and constructors are implemented public boolean equals(Object obj) { if (obj == this) return true; if (!(obj instanceof Politician)) return false; Politician pol = (Politician)obj; boolean returnVal = (this.firstName+this.lastName).equals(pol.firstName+pol.lastName)); return return Val; } public int hashCode() { return lastName.hashCode(); //last name is a String, so lastName.hashCode() is defined in the String implementatior } }

Computer Networking: A Top-Down Approach (7th Edition)
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
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**Does the following class satisfy the Java Hash Code contract? Explain.** ```java public class Politician { String firstName; String lastName; //…assume other fields and constructors are implemented public boolean equals(Object obj) { if (obj == this) return true; if (!(obj instanceof Politician)) return false; Politician pol = (Politician) obj; boolean returnVal = (this.firstName + this.lastName) .equals(pol.firstName + pol.lastName); return returnVal; } public int hashCode() { return lastName.hashCode(); // lastName is a String, so lastName.hashCode() is defined in the String implementation } } ``` ### Analysis This Java class, `Politician`, defines two fields: `firstName` and `lastName`. The `equals` method checks if an object is equal based on the combination of `firstName` and `lastName`. However, the `hashCode` method relies solely on `lastName`. ### Hash Code Contract The Java hash code contract states that: 1. If two objects are equal according to the `equals(Object)` method, then calling `hashCode` on each of the two objects must produce the same integer result. 2. If two objects are not equal according to the `equals(Object)` method, it is not required that calling `hashCode` on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing the same integer results for unequal objects may impact the performance of hash tables. ### Explanation: - **Equality Check in `equals` Method:** This method checks equality based on both `firstName` and `lastName`. - **Hash Code Calculation in `hashCode` Method:** This method only uses `lastName` to compute the hashCode. Because `hashCode` doesn't consider `firstName`, there might be cases where two `Politician` objects are considered equal (`equals` method returns true) but produce different hash codes if their `lastName` fields are the same while their `firstName` fields differ. This violates the hash code contract, leading to potential issues in hash-based collections like `HashMap` or `HashSet`. To satisfy the contract, the `hashCode` method should involve both `firstName` and `lastName` in the computation
Transcribed Image Text:**Does the following class satisfy the Java Hash Code contract? Explain.** ```java public class Politician { String firstName; String lastName; //…assume other fields and constructors are implemented public boolean equals(Object obj) { if (obj == this) return true; if (!(obj instanceof Politician)) return false; Politician pol = (Politician) obj; boolean returnVal = (this.firstName + this.lastName) .equals(pol.firstName + pol.lastName); return returnVal; } public int hashCode() { return lastName.hashCode(); // lastName is a String, so lastName.hashCode() is defined in the String implementation } } ``` ### Analysis This Java class, `Politician`, defines two fields: `firstName` and `lastName`. The `equals` method checks if an object is equal based on the combination of `firstName` and `lastName`. However, the `hashCode` method relies solely on `lastName`. ### Hash Code Contract The Java hash code contract states that: 1. If two objects are equal according to the `equals(Object)` method, then calling `hashCode` on each of the two objects must produce the same integer result. 2. If two objects are not equal according to the `equals(Object)` method, it is not required that calling `hashCode` on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing the same integer results for unequal objects may impact the performance of hash tables. ### Explanation: - **Equality Check in `equals` Method:** This method checks equality based on both `firstName` and `lastName`. - **Hash Code Calculation in `hashCode` Method:** This method only uses `lastName` to compute the hashCode. Because `hashCode` doesn't consider `firstName`, there might be cases where two `Politician` objects are considered equal (`equals` method returns true) but produce different hash codes if their `lastName` fields are the same while their `firstName` fields differ. This violates the hash code contract, leading to potential issues in hash-based collections like `HashMap` or `HashSet`. To satisfy the contract, the `hashCode` method should involve both `firstName` and `lastName` in the computation
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