单项选择题
程序员正在进行一个项目,必须实现equals方法与所给的hashCode方法协调运行:
public int hashCode() {
return (size.hashCode() + color.hashCode()) * 17;
}
哪一个equals方法支持此目标?()
A. 无法确定
B. public boolean equals(Object o) { Sock s = (Sock) o; return size.equals(s.size);}
C. public boolean equals(Object o) { Sock s = (Sock) o; return color.equals(s.color);}
D. public boolean equals(Object o) { Sock s = (Sock) o; return size.equals(s.size) &&color.equals(s.color); }
点击查看答案&解析
相关考题
-
单项选择题
现有: 1. class Alpha { void m1() {} } 2. class Beta extends Alpha { void m2() { } } 3. class Gamma extends Beta { } 4. 5. class GreekTest { 6. public static void main(String [] args) { 7. Alpha [] a = {new Alpha(), new Beta(), new Gamma() }; 8. for(Alpha a2 : a) { 9. a2.m1(); 10. if (a2 instanceof Beta || a2 instanceof Gamma) 11. //insert code here 12. } 13. } 14. } 哪一行代码插入到第11行,将编译但是会在运行时产生异常?()
A. a2.m2();
B. ((Beta)a2).m2();
C. ((Alpha)a2).m2();
D. ((Gamma)a2).m2(); -
单项选择题
public class Pet{ private String name; public Pet(String name){ this.name = name; } public void speak(){ System.out.print(name); } } public class Dog extends Pet{ public Dog(String name){ super(name); } public void speak(){ super.speak(); System.out.print(“ Dog ”); } } 执行代码 Pet pet = new Dog(“京巴”); pet.speak(); 后输出的内容是哪项?()
A. 京巴
B. 京巴 Dog
C. null
D. Dog京巴 -
单项选择题
程序: class MyDate{ private int year; private int month; private int day; public MyDate(int year,int month,int day){ this.year=year; this.month=month; this.day=day; } //Override Method } 为了让new MyDate(1980,11,9)==new MyDate(1980,11,9) 返回true,必须在Override Method处覆盖哪个方法?()
A. hashCode
B. equals
C. toString
D. notify
