java基础学习日志16
集合
List
public class Student implements Comparable {
String name;
int 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;
}
public Student(String name,int age) {
this.name= name;
this.age=age;
}
@Override
public int compareTo(Student o) {
System.out.println("hello compareTo");
return o.age-this.age;
}
}
import java.util.Comparator;
public class StudentComparator implements Comparator{
@Override
public int compare(Student o1, Student o2) {
return o1.name.compareTo(o2.name);
}
} import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class ListDem1 {
public static void main(String[] args) {
String person1 = "1zhangsan";
String person2 = "2li4";
String person3 = "3wang5";
String person4 = "4zhao6";
List list = new ArrayList<>();
list.add(person1);
list.add(person2);
list.add(person3);
list.add(person4);
// Collections.sort(list);
// for(int i=list.size()-1;i>=0;i--){
// if(list.get(i).equals("zhangsan")){
// list.remove(i);
// }
// System.out.print(list.get(i)+"\t");
// }
// list = new CopyOnWriteArrayList<>(list);
// int i=0;
// for(String str:list){
// if(str.equals("zhangsan")){
// list.remove(str);
// }
// }
// System.out.print(list.toString());
Student stu1 = new Student("a孙勇", 18);
Student stu2 = new Student("d李凯伦", 12);
Student stu3 = new Student("f李南", 9);
Student stu4 = new Student("d杨东旭", 3);
Student stu5 = new Student("h丁浩天", 3);
Student stu6 = new Student("e冯苏州", 12);
Student stu7 = new Student("q任峻成", 17);
Student stu8 = new Student("h陈杰", 19);
Student stu9 = new Student("k梁跃博", 16);
Student stu10 = new Student("z李炜业", 16);
List stulist = new ArrayList();
stulist.add(stu1);
stulist.add(stu2);
stulist.add(stu3);
stulist.add(stu4);
stulist.add(stu5);
stulist.add(stu6);
stulist.add(stu7);
stulist.add(stu8);
stulist.add(stu9);
stulist.add(stu10);
Collections.sort(stulist);
for (int i = 0; i < stulist.size(); i++) {
System.out.println(stulist.get(i).name + "\t" + stulist.get(i).getAge());
}
Collections.sort(stulist, new StudentComparator());
System.out.println("--------------------------------------------");
for (int i = 0; i < stulist.size(); i++) {
System.out.println(stulist.get(i).name + "\t" + stulist.get(i).getAge());
}
Collections.sort(stulist, new StudentComparator() {
public int compare(Student o1, Student o2) {
return o1.getName().length() - o2.getName().length();
}
});
System.out.println("--------------------------------------------");
for (int i = 0; i < stulist.size(); i++) {
System.out.println(stulist.get(i).name + "\t" + stulist.get(i).getAge());
}
}
}
Set
import java.util.Comparator;
public class Student implements Comparable,Comparator{
private String name;
private int age;
public Student(String name ,int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String nam) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
//比较年龄大小，重写
@Override
public int compareTo(Student o) {
return this.age-o.age;
}
//比较字符第一个字母排序，重写
@Override
public int compare(Student o1, Student o2) {
return o1.name.compareTo(o2.name);
}
//set中要去重，重写
@Override
public int hashCode() {
System.out.println("这还是equals方法");
final int prime = 31;
int result = 1;
result = prime * result + age;
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 (name == null) {
if (other.name != null)
return false;
} else if (!name.equals(other.name))
return false;
return true;
}
}
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
public class SetDemo {
public static void main(String[] args) {
// Set set = new HashSet<>();
String str = "tom";
String str1 = "tom1";
String str2 = "tom2";
String str3 = "tom";
// set.add(str);
// set.add(str1);
// set.add(str2);
// set.add(str3);
// Iterator it = set.iterator();
// while (it.hasNext()) {
// System.out.println(it.next());
// }
//想要去重，在Student里重写equals
Set stuSet = new HashSet<>();
Student stu = new Student("tom1", 12);
Student stu1 = new Student("tom2", 12);
Student stu2 = new Student("tom", 12);
Student stu3 = new Student("tom", 12);
stuSet.add(stu);
stuSet.add(stu1);
stuSet.add(stu2);
stuSet.add(stu3);
Iterator stuit = stuSet.iterator();
while (stuit.hasNext()) {
System.out.println(stuit.next().getName());
}
}
}
import java.util.Iterator;
import java.util.TreeSet;
public class TreeSetDemo {
public static void main(String[] args) {
TreeSet pset = new TreeSet();
Person p1 = new Person("tom",12);
Person p2 = new Person("jerry",14);
Person p3 = new Person("jack",19);
Person p4 = new Person("rose",21);
Person p5 = new Person("rose",21);
pset.add(p1);
pset.add(p2);
pset.add(p3);
pset.add(p4);
pset.add(p5);
Iterator pit = pset.iterator();
while(pit.hasNext()){
Person p = pit.next();
System.out.println(p.getName()+"\t"+p.getAge());
}
}
}
Map
public class Person implements Comparable {
private String name;
private int age;
public Person(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(Person o) {
// // TODO Auto-generated method stub
// return this.age - o.age;
// }
//光比较年龄大小有局限性，重写方法，增加其他变量的比较，用conpareTo
public int compareTo(Person person) {
if (this.age != person.age) {
return this.age - person.age;
} else {
return this.name.compareTo(person.name);
}
}
//// 没调用，不需要重写
// @Override
// public int hashCode() {
// System.out.println("这是equals方法");
// final int prime = 31;
// int result = 1;
// result = prime * result + age;
// result = prime * result + ((name == null) ? 0 : name.hashCode());
// return result;
// }
//
// @Override
// public boolean equals(Object obj) {
// System.out.println("hello this is equals");
// if (this == obj)
// return true;
// if (obj == null)
// return false;
// if (getClass() != obj.getClass())
// return false;
// Person other = (Person) obj;
// if (age != other.age)
// return false;
// if (name == null) {
// if (other.name != null)
// return false;
// } else if (!name.equals(other.name))
// return false;
// return true;
// }
}
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
public class MapDemo {
public static void main(String[] args) {
Map person = new HashMap<>();
Person per1 = new Person("自行车", 98);
Person per2 = new Person("九八", 97);
Person per3 = new Person("阿拉斯加", 876);
Person per4 = new Person("柴犬", 9);
person.put(1, per1);
person.put(2, per2);
person.put(4, per3);
person.put(3, per4);
//通过值遍历
// Collection a = person.values();
// for (Person per : a) {
// Person p = per;
// System.out.println(p.getName()+"\t"+p.getAge());
// }
//通过键值遍历
// Set set = person.keySet();
// for (Integer per:set ) {
// System.out.println(per+":"+person.get(per).getAge());
// }
//通过entry遍历
for(Entry en : person.entrySet()){
System.out.println(en.getKey()+":"+en.getValue().getName()+"\t"+en.getValue().getAge());
}
}
}