import java.util.*;public class EqualsTest
{
public static void main(String[] args)
{
Employee alice1 = new Employee("Alice Adams", 75000, 1987, 12, 15);
Employee alice2 = alice1;
Employee alice3 = new Employee("Alice Adams", 75000, 1987, 12, 15);
Employee bob = new Employee("Bob Brandson", 50000, 1989, 10, 1); System.out.println("alice1 == alice2: " + (alice1 == alice2)); System.out.println("alice1 == alice3: " + (alice1 == alice3)); System.out.println("alice1.equals(alice3): " + alice1.equals(alice3)); System.out.println("alice1.equals(bob): " + alice1.equals(bob)); System.out.println("bob.toString(): " + bob); Manager carl = new Manager("Carl Cracker", 80000, 1987, 12, 15);
Manager boss = new Manager("Carl Cracker", 80000, 1987, 12, 15);
boss.setBonus(5000);
System.out.println("boss.toString(): " + boss);
System.out.println("carl.equals(boss): " + carl.equals(boss));
System.out.println("alice1.hashCode(): " + alice1.hashCode());
System.out.println("alice3.hashCode(): " + alice3.hashCode());
System.out.println("bob.hashCode(): " + bob.hashCode());
System.out.println("carl.hashCode(): " + carl.hashCode());
}
}class Employee
{
public Employee(String n, double s, int year, int month, int day)
{
name = n;
salary = s;
GregorianCalendar calendar = new GregorianCalendar(year, month - 1, day);
hireDay = calendar.getTime();
} public String getName()
{
return name;
} public double getSalary()
{
return salary;
} public Date getHireDay()
{
return hireDay;
} public void raiseSalary(double byPercent)
{
double raise = salary * byPercent / 100;
salary += raise;
} public boolean equals(Object otherObject)
{
// a quick test to see if the objects are identical
if (this == otherObject) return true; // must return false if the explicit parameter is null
if (otherObject == null) return false; // if the classes don't match, they can't be equal
if (getClass() != otherObject.getClass())
return false; // now we know otherObject is a non-null Employee
Employee other = (Employee) otherObject; // test whether the fields have identical values
return name.equals(other.name)
&& salary == other.salary
&& hireDay.equals(other.hireDay);
} public int hashCode()
{
return 7 * name.hashCode()
+ 11 * new Double(salary).hashCode()
+ 13 * hireDay.hashCode();
} public String toString()
{
return getClass().getName()
+ "[name=" + name
+ ",salary=" + salary
+ ",hireDay=" + hireDay
+ "]";
} private String name;
private double salary;
private Date hireDay;
}class Manager extends Employee
{
public Manager(String n, double s, int year, int month, int day)
{
super(n, s, year, month, day);
bonus = 0;
} public double getSalary()
{
double baseSalary = super.getSalary();
return baseSalary + bonus;
} public void setBonus(double b)
{
bonus = b;
} public boolean equals(Object otherObject)
{
if (!super.equals(otherObject)) return false;
Manager other = (Manager) otherObject;
// super.equals checked that this and other belong to the same class
return bonus == other.bonus;
} public int hashCode()
{
return super.hashCode()
+ 17 * new Double(bonus).hashCode();
} public String toString()
{
return super.toString()
+ "[bonus=" + bonus
+ "]";
} private double bonus;
}
System.out.println("bob.toString(): " + bob);
这个 最后结果是输出了bob的name salary 和 日期 为啥bob变量直接输出的是tostring的内容(只有一个bob)
{
public static void main(String[] args)
{
Employee alice1 = new Employee("Alice Adams", 75000, 1987, 12, 15);
Employee alice2 = alice1;
Employee alice3 = new Employee("Alice Adams", 75000, 1987, 12, 15);
Employee bob = new Employee("Bob Brandson", 50000, 1989, 10, 1); System.out.println("alice1 == alice2: " + (alice1 == alice2)); System.out.println("alice1 == alice3: " + (alice1 == alice3)); System.out.println("alice1.equals(alice3): " + alice1.equals(alice3)); System.out.println("alice1.equals(bob): " + alice1.equals(bob)); System.out.println("bob.toString(): " + bob); Manager carl = new Manager("Carl Cracker", 80000, 1987, 12, 15);
Manager boss = new Manager("Carl Cracker", 80000, 1987, 12, 15);
boss.setBonus(5000);
System.out.println("boss.toString(): " + boss);
System.out.println("carl.equals(boss): " + carl.equals(boss));
System.out.println("alice1.hashCode(): " + alice1.hashCode());
System.out.println("alice3.hashCode(): " + alice3.hashCode());
System.out.println("bob.hashCode(): " + bob.hashCode());
System.out.println("carl.hashCode(): " + carl.hashCode());
}
}class Employee
{
public Employee(String n, double s, int year, int month, int day)
{
name = n;
salary = s;
GregorianCalendar calendar = new GregorianCalendar(year, month - 1, day);
hireDay = calendar.getTime();
} public String getName()
{
return name;
} public double getSalary()
{
return salary;
} public Date getHireDay()
{
return hireDay;
} public void raiseSalary(double byPercent)
{
double raise = salary * byPercent / 100;
salary += raise;
} public boolean equals(Object otherObject)
{
// a quick test to see if the objects are identical
if (this == otherObject) return true; // must return false if the explicit parameter is null
if (otherObject == null) return false; // if the classes don't match, they can't be equal
if (getClass() != otherObject.getClass())
return false; // now we know otherObject is a non-null Employee
Employee other = (Employee) otherObject; // test whether the fields have identical values
return name.equals(other.name)
&& salary == other.salary
&& hireDay.equals(other.hireDay);
} public int hashCode()
{
return 7 * name.hashCode()
+ 11 * new Double(salary).hashCode()
+ 13 * hireDay.hashCode();
} public String toString()
{
return getClass().getName()
+ "[name=" + name
+ ",salary=" + salary
+ ",hireDay=" + hireDay
+ "]";
} private String name;
private double salary;
private Date hireDay;
}class Manager extends Employee
{
public Manager(String n, double s, int year, int month, int day)
{
super(n, s, year, month, day);
bonus = 0;
} public double getSalary()
{
double baseSalary = super.getSalary();
return baseSalary + bonus;
} public void setBonus(double b)
{
bonus = b;
} public boolean equals(Object otherObject)
{
if (!super.equals(otherObject)) return false;
Manager other = (Manager) otherObject;
// super.equals checked that this and other belong to the same class
return bonus == other.bonus;
} public int hashCode()
{
return super.hashCode()
+ 17 * new Double(bonus).hashCode();
} public String toString()
{
return super.toString()
+ "[bonus=" + bonus
+ "]";
} private double bonus;
}
System.out.println("bob.toString(): " + bob);
这个 最后结果是输出了bob的name salary 和 日期 为啥bob变量直接输出的是tostring的内容(只有一个bob)
* Prints an Object and then terminate the line. This method calls
* at first String.valueOf(x) to get the printed object's string value,
* then behaves as
* though it invokes <code>{@link #print(String)}</code> and then
* <code>{@link #println()}</code>.
*
* @param x The <code>Object</code> to be printed.
*/
public void println(Object x) {
String s = String.valueOf(x);
synchronized (this) {
print(s);
newLine();
}
}这个是System.out.println();的源代码,默认的时候调用String.valueOf(x),所以返回的是对象的toString