單項(xiàng)選擇題

1. public class Person {
2. private String name；
3. public Person（String name） { this.name = name； }
4. public boolean equals（Person p） {
5. return p.name.equals（this.name）；
6. }
7. }
Which is true？（）

A. The equals method does NOT properly override the Object.equals method.
B. Compilation fails because the private attribute p.name cannot be accessed in line 5.
C. To work correctly with hash-based data structures， this class must also implement the hashCode method.
D. When adding Person objects to a java.util.Set collection， the equals method in line 4 will prevent duplicates.

你可能感興趣的試題

單項(xiàng)選擇題

public class Person {
private name；
public Person（String name） {
this.name = name；
}
public boolean equals（Object o） {
if（ !o instanceof Person ） return false；
Person p = （Person） o；
return p.name.equals（this.name）；
}
}
Which is true？（）

A. Compilation fails because the hashCode method is not overridden.
B. A HashSet could contain multiple Person objects with the same name.
C. All Person objects will have the same hash code because the hashCode method is not overridden.
D. If a HashSet contains more than one Person object with name=”Fred”， then removing another person， also with name=”Fred”， will remove them all.

多項(xiàng)選擇題

public class Key {
private long id1；
private long 1d2；
// class Key methods
}
A programmer is developing a class Key， that will be used as a key in a standard java.util.HashMap. Which two methods should be overridden to assure that Key works correctly as a key？（）

A. public int hashCode（）
B. public boolean equals（Key k）
C. public int compareTo（Object o）
D. public boolean equals（Object o）
E. public boolean compareTo（Key k）

1. public class Person { 2. private String name； 3. public Person（String name） { this.name = name； } 4. public boolean equals（Person p） { 5. return p.name.equals（this.name）； 6. } 7. } Which is true？（）

你可能感興趣的試題

public class Person { private name； public Person（String name） { this.name = name； } public boolean equals（Object o） { if（ !o instanceof Person ） return false； Person p = （Person） o； return p.name.equals（this.name）； } } Which is true？（）

public class Key { private long id1； private long 1d2； // class Key methods } A programmer is developing a class Key， that will be used as a key in a standard java.util.HashMap. Which two methods should be overridden to assure that Key works correctly as a key？（）

1. public class Person {
2. private String name；
3. public Person（String name） { this.name = name； }
4. public boolean equals（Person p） {
5. return p.name.equals（this.name）；
6. }
7. }
Which is true？（）

public class Person {
private name；
public Person（String name） {
this.name = name；
}
public boolean equals（Object o） {
if（ !o instanceof Person ） return false；
Person p = （Person） o；
return p.name.equals（this.name）；
}
}
Which is true？（）

public class Key {
private long id1；
private long 1d2；
// class Key methods
}
A programmer is developing a class Key， that will be used as a key in a standard java.util.HashMap. Which two methods should be overridden to assure that Key works correctly as a key？（）