Question

Java 怎么用compareTo接口实现排序

我有一个Book类，代码如下：
public class Book
{
private String authorfirstname;
private String title;
private String borrowedperson;
private boolean loan;
private String authorsurname;
public Book(String title,String authorfirstname, String authorsurname, String borrowedperson, boolean loan)
{
this.title = title;
this.authorfirstname = authorfirstname;
this.authorsurname = authorsurname;
this.borrowedperson = borrowedperson;
this.loan = loan;
}
public String getauthorfirstname()
{
return authorfirstname;
}
public String gettitle()
{
return title;
}
public String getborrowedperson()
{
return this.borrowedperson;
}
public boolean getloan()
{
return loan;
}
然后再另一个类中定义了一个数组a,储存了好多Book类型的元素。
现在要求用compareTo接口对Book类中的authorsurname进行升序排序，求大神告知如何排啊

Answer 1

package test;

public class Field implements Comparable<Field> {

    private String name;
    private int age;

    public Field() {
    }
    public Field(String name, int age) {
        this.name = name;
        this.age = age;
    }
    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;
    }

    @Override
    public int compareTo(Field o) {
        // 先按age排序
        if (this.age > o.getAge()) {
            return (this.age - o.getAge());
        }
        if (this.age < o.getAge()) {
            return (this.age - o.getAge());
        }
        // 按name排序
        if (this.name.compareTo(o.getName()) > 0) {
            return 1;
        }
        if (this.name.compareTo(o.getName()) < 0) {
            return -1;
        }
        return 0;
    }
}

Answer 2

public class Book implements Comparable
{
private String authorfirstname;
private String title;
private String borrowedperson;
private boolean loan;
private String authorsurname;
public Book(String title,String authorfirstname, String authorsurname, String borrowedperson, boolean loan)
{
this.title = title;
this.authorfirstname = authorfirstname;
this.authorsurname = authorsurname;
this.borrowedperson = borrowedperson;
this.loan = loan;
}
public String getauthorfirstname()
{
return authorfirstname;
}
public String gettitle()
{
return title;
}
public String getborrowedperson()
{
return this.borrowedperson;
}
public boolean getloan()
{
return loan;
}
@Override
public int compareTo(Object o)
{
// 自己写条件
return 0;
}
}
希望采纳

追问

条件怎么写，我刚开始学不太会，这个类我只要求对authorsurname一个量进行排序

追答

那就判断这个条件啊

Answer 3

Collections.sort(list, new Comparator() {
public int compare(Object a, Object b) {
int one = ((Book)a).getBookId ();
int two = ((Book)b).getBookId ();
return one- two ;
}
});

追问

看不懂，你这是写在Book这个类里吗

追答

API：