对象排序

参考链接：

https://docs.oracle.com/javase/tutorial/collections/interfaces/order.html

排序的对象类型需要实现Comparable接口 或 Comparator接口

package bill99.com.jdk18;

public class Student implements Comparable<Student>{
	
	public Student(String name, int age, String className, int grade) {
		super();
		this.name = name;
		this.age = age;
		this.className = className;
		this.grade = grade;
	}
	
	
	private String name;
	private int age;
	private String className;
	
	private  int grade;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public String getClassName() {
		return className;
	}
	public void setClassName(String className) {
		this.className = className;
	}
	
	public int getGrade() {
		return grade;
	}
	public void setGrade(int grade) {
		this.grade = grade;
	}
	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + age;
		result = prime * result + ((className == null) ? 0 : className.hashCode());
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		return result;
	}
	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Student other = (Student) obj;
		if (age != other.age)
			return false;
		if (className == null) {
			if (other.className != null)
				return false;
		} else if (!className.equals(other.className))
			return false;
		if (name == null) {
			if (other.name != null)
				return false;
		} else if (!name.equals(other.name))
			return false;
		return true;
	}
	public int compareTo(Student o) {
		
		/**
		 *  return (e1.number() < e2.number() ? -1 :
               (e1.number() == e2.number() ? 0 : 1));
		 */
		int   result = 0;
		//判断属性的值的问题
		if(this.getGrade()>o.getGrade()){
			result =1;
		}
		if(this.getGrade() < o.getGrade()){
			result =-1;
		}
		return result;
	}
	@Override
	public String toString() {
		return "Student [name=" + name + ", age=" + age + ", className=" + className + ", grade=" + grade + "]";
	}
	
	
	
	
}