Java中List對象集合按對象中某字段進行排序舉例
在Java中,可以使用List集合對象的sort(Comparator<? super E> c)方法,按照對象中某字段對List集合進行排序
default void sort(Comparator<? super E> c) { Object[] a = this.toArray(); Arrays.sort(a, (Comparator) c); ListIterator<E> i = this.listIterator(); for (Object e : a) { i.next(); i.set((E) e); } }
栗子:
import java.util.*; import java.util.stream.Collectors; public class StreamTest { public static void main(String[] args) { List<Person2> personList = new ArrayList<Person2>(); personList.add(new Person2("Tom", 8900, 18,"male", "A")); personList.add(new Person2("Jack", 7000, 19,"male", "A")); personList.add(new Person2("Lily", 7800, 20,"female", "D")); personList.add(new Person2("Anni", 8200, 18,"female", "B")); personList.add(new Person2("Owen", 9500, 23,"male", "D")); personList.add(new Person2("Alisa", 7900, 28,"female", "C")); //根據(jù)List集合對象的sort方法(語句后x.get與y.get調(diào)換位置即為倒序) personList.sort((x,y) -> Integer.compare(x.getSalary(),y.getSalary()));//int類型正序 personList.forEach(System.out::println); System.out.println("================================"); personList.sort((a, b) -> a.getSalary() - b.getSalary());//int類型正序 personList.forEach(System.out::println); System.out.println("================================"); personList.sort(Comparator.comparing(Person2::getSalary));//int類型正序排序 personList.forEach(System.out::println); System.out.println("================================"); personList.sort((a,b) -> a.getLevel().compareTo(b.getLevel()));//其他類型正序 personList.forEach(System.out::println); System.out.println("================================"); //stream流的sorted方法正序排序(倒序:Comparator.comparing(Person2::getSalary).reversed()) personList = personList.stream().sorted(Comparator.comparing(Person2::getSalary)).collect(Collectors.toList()); personList.forEach(System.out::println); System.out.println("================================"); } } class Person2 { private String name; // 姓名 private int salary; // 薪資 private int age; // 年齡 private String sex; //性別 private String level; // 級別 // 構(gòu)造方法 public Person2(String name, int salary, int age, String sex, String level) { this.name = name; this.salary = salary; this.age = age; this.sex = sex; this.level = level; } // 省略了get和set,請自行添加 public String getName() { return name; } public void setName(String name) { this.name = name; } public int getSalary() { return salary; } public void setSalary(int salary) { this.salary = salary; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } public String getLevel() { return level; } public void setLevel(String level) { this.level = level; } @Override public String toString() { return "Person2{" + "name=" + name + ", salary='" + salary + '\'' + ", age='" + age + '\'' + ", sex='" + sex + '\'' + ", level=" + level + '}'; } }
打印輸出結(jié)果如下:
Person2{name=Jack, salary='7000', age='19', sex='male', level=A}
Person2{name=Lily, salary='7800', age='20', sex='female', level=D}
Person2{name=Alisa, salary='7900', age='28', sex='female', level=C}
Person2{name=Anni, salary='8200', age='18', sex='female', level=B}
Person2{name=Tom, salary='8900', age='18', sex='male', level=A}
Person2{name=Owen, salary='9500', age='23', sex='male', level=D}
================================
Person2{name=Jack, salary='7000', age='19', sex='male', level=A}
Person2{name=Lily, salary='7800', age='20', sex='female', level=D}
Person2{name=Alisa, salary='7900', age='28', sex='female', level=C}
Person2{name=Anni, salary='8200', age='18', sex='female', level=B}
Person2{name=Tom, salary='8900', age='18', sex='male', level=A}
Person2{name=Owen, salary='9500', age='23', sex='male', level=D}
================================
Person2{name=Jack, salary='7000', age='19', sex='male', level=A}
Person2{name=Lily, salary='7800', age='20', sex='female', level=D}
Person2{name=Alisa, salary='7900', age='28', sex='female', level=C}
Person2{name=Anni, salary='8200', age='18', sex='female', level=B}
Person2{name=Tom, salary='8900', age='18', sex='male', level=A}
Person2{name=Owen, salary='9500', age='23', sex='male', level=D}
================================
Person2{name=Jack, salary='7000', age='19', sex='male', level=A}
Person2{name=Tom, salary='8900', age='18', sex='male', level=A}
Person2{name=Anni, salary='8200', age='18', sex='female', level=B}
Person2{name=Alisa, salary='7900', age='28', sex='female', level=C}
Person2{name=Lily, salary='7800', age='20', sex='female', level=D}
Person2{name=Owen, salary='9500', age='23', sex='male', level=D}
================================
Person2{name=Jack, salary='7000', age='19', sex='male', level=A}
Person2{name=Lily, salary='7800', age='20', sex='female', level=D}
Person2{name=Alisa, salary='7900', age='28', sex='female', level=C}
Person2{name=Anni, salary='8200', age='18', sex='female', level=B}
Person2{name=Tom, salary='8900', age='18', sex='male', level=A}
Person2{name=Owen, salary='9500', age='23', sex='male', level=D}
================================
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