黑马程序员——集合——Set集合,增强for循环,数据结构,泛型,Collections集合工具类

<span style="font-family:FangSong_GB2312;font-size:18px;"><strong><span style="font-family:KaiTi_GB2312;font-size:18px;">package cn.itcast;

import java.util.HashSet;

public class Test2 {

/**
* HashSet存储字符串并遍历(String类已经重写了hashCode()和equals()方法)
*/
public static void main(String[] args) {
//创建集合对象
HashSet<String>  hs = new HashSet<String>();

//创建元素对象
String s = "火影忍者";
String s2 = "海贼王";
String s3 = "灌篮高手";
String s4 = "柯南";

//将元素对象添加进集合
hs.add(s);
hs.add(s2);
hs.add(s3);
hs.add(s4);

//使用增强for循环遍历HashSet集合
for (String string : hs) {
//输出遍历后的结果
System.out.println(string);
}
}

}
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<span style="font-family:FangSong_GB2312;font-size:18px;"><strong><span style="font-family:KaiTi_GB2312;font-size:18px;">package cn.itcast;

public class Student{

private String name;
private int  age;
public Student() {
super();

}
public Student(String name, int age) {
super();
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 String toString() {
return "Student [name=" + name + ", age=" + age + "]";
}
@Override
public int hashCode() {
System.out.println("hashCode");
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("equals");
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;
}

}
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<span style="font-family:FangSong_GB2312;font-size:18px;"><strong><span style="font-family:KaiTi_GB2312;font-size:18px;">package cn.itcast;

import java.util.HashSet;
import java.util.Iterator;

public class Test {

/**
* Set集合特点：无序的，不可重复的   Set是接口，操作必须由子类实现
* 使用HashSet创建集合并进行操作
* 通过修改类中的hashCode方法以及equals方法避免了重复元素的出现
*/
public static void main(String[] args) {
//创建HashSet集合对象
HashSet hs =new HashSet();

//创建元素对象
Student s = new Student("貂蝉",13);
Student s2 = new Student("王昭君",23);
Student s3 = new Student("西施",15);
Student s4 = new Student("杨玉环",50);

//将元素添加进集合
hs.add(s);
hs.add(s);
hs.add(s2);
hs.add(s3);
hs.add(s4);
hs.add(new Student("杨玉环",50));

//返回迭代器,对集合进行遍历
Iterator iterator = hs.iterator();
//使用hasNext方法查询元素,next获取元素
while (iterator.hasNext()) {
Student student = (Student) iterator.next();
System.out.println(student);
}

}

}
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<span style="font-family:FangSong_GB2312;font-size:18px;"><strong><span style="font-family:KaiTi_GB2312;font-size:18px;">package cn.itcast;

import java.util.Iterator;
import java.util.TreeSet;

public class Test3 {

/**
* TreeSet存储字符串并遍历。(String已经实现了Comparable接口)
*/
public static void main(String[] args) {
//创建TreeSet集合对象
TreeSet<String> ts = new TreeSet<String>();

//创建元素对象
String s ="wcba";
String s2 ="nba";
String s3 ="cba";

//将元素对象添加进集合
ts.add(s);
ts.add(s2);
ts.add(s3);

//遍历集合
//返回迭代器
Iterator<String> iterator = ts.iterator();
//通过迭代器的hasNext方法查询元素,next方法获取元素
while (iterator.hasNext()) {
String string = iterator.next();
//输出遍历结果
System.out.println(string);
}

}

}
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<span style="font-family:FangSong_GB2312;font-size:18px;"><strong><span style="font-family:KaiTi_GB2312;font-size:18px;">package cn.itcast;

public class Person {

private String name;
private int age;
public Person() {
super();

}
public Person(String name, int age) {
super();
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 String toString() {
return "Person [name=" + name + ", age=" + age + "]";
}

}
</span></strong></span>

<span style="font-family:FangSong_GB2312;font-size:18px;"><strong><span style="font-family:KaiTi_GB2312;font-size:18px;">package cn.itcast;

import java.util.Comparator;
import java.util.TreeSet;

public class Test4 {

/**
* TreeSet集合的使用
* 比较器排序:
* 集合实现Comparator接口,集合就有了比较性
* 重写Comparator中的compare方法
* 使用匿名内部类完成比较器的实现
*/
public static void main(String[] args) {

//创建集合对象
TreeSet ts = new TreeSet(new Comparator(){

public int compare(Object o1,Object o2){

Person p = (Person)o1;
Person p2 = (Person)o2;

int result ;
result =p.getAge()-p2.getAge();
if (result==0) {
result = p.getName().compareTo(p.getName());
}
return result;

}
});

//创建集合元素
Person p = new Person("林黛玉",19);
Person p2 = new Person("贾宝玉",21);
Person p3 = new Person("薛宝钗",18);
Person p4 = new Person("王熙凤",30);

//将元素添加进集合
ts.add(p);
ts.add(p2);
ts.add(p3);
ts.add(p3);
ts.add(p4);
ts.add(new Person("贾宝玉",21));

//使用增强for循环遍历集合
for(Object person :ts){

System.out.println(person);
}

}

}
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