java--集合案例

àì夳堔傛蜴生んèń 2022-06-03 08:38 160阅读 0赞

**案例一 ：**

**简单回顾：**

@Test  
public void test3()\{  
List<Integer> list=new ArrayList<Integer>();  
list.add(15);  
list.add(343);  
list.add(43);  
list.add(13);  
list.add(5);  
list.add(75);  
Collections.sort(list);  
//System.out.println("排序后："+list);

System.out.println("最大值："+Collections.max(list));  
System.out.println("最小值："+Collections.min(list));  
Collections.replaceAll(list, 75, 88);  
  
for(int i:list)\{  
System.out.println(i);  
\}  
\}

**Fruit:**

package Test;  
  
  
public class Ft **implements Comparable<Ft>**\{  
private String name;  
private int price;  
  
public Ft(String name, int price) \{  
this.name = name;  
this.price = price;  
\}  
public String getName() \{  
return name;  
\}  
public void setName(String name) \{  
this.name = name;  
\}  
public int getPrice() \{  
return price;  
\}  
public void setPrice(int price) \{  
this.price = price;  
\}  
@Override  
public int compareTo(Ft o) \{  
if(this.price>o.getPrice())\{  
return 1;  
\}else\{  
return -1;  
\}  
\}  
  
  
\}

**test:**

@Test  
public void test2()\{  
Map<String,Integer> map=new HashMap<String, Integer>();  
Scanner sc=new Scanner(System.in);  
for(int i=0;i<5;i++)\{  
System.out.println("请输入水果名称：");  
String name=sc.next();  
System.out.println("请输入价格：");  
int price=sc.nextInt();  
map.put(name, price);  
\}  
print(map);  
List<Ft> list=new ArrayList<Ft>();  
Set<String> smk=map.keySet();  
Iterator<String> iter=smk.iterator();  
while(iter.hasNext())\{  
String key=iter.next();  
int value=map.get(key);  
if(value>=5)\{  
Ft f1=new Ft(key, value);  
list.add(f1);  
\}  
\}  
System.out.println("\#\#\#\#\#\#\#\#\#\#\#");  
  
/\*for(int i=0;i<list.size();i++)\{  
for(int j=0;j<list.size()-1-i;j++)\{  
if(list.get(j).getPrice()>list.get(j+1).getPrice())\{  
Ft tmp=list.get(j);  
list.set(j, list.get(j+1));  
list.set(j+1, tmp);  
\}  
\}  
\}\*/  
  
Collections.sort(list);**//排序方法**

for(Ft f:list)\{  
System.out.println("水果："+f.getName()+"，价格："+f.getPrice());  
\}  
  
\}

private void print(Map<String,Integer> map)\{  
Set<Entry<String, Integer>> entryset=map.entrySet();  
for(Entry<String, Integer> en:entryset)\{  
System.out.println("水果："+en.getKey()+",价格："+en.getValue());  
\}  
\}

**案例二：**

**User:**

package Test;  
  
  
public class User implements Comparable<User> \{  
private String name;  
private int age;  
private String sex;  
  
public User(String name, int age, String sex) \{  
this.name = name;  
this.age = age;  
this.sex = sex;  
\}  
  
  
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 getSex() \{  
return sex;  
\}  
  
  
public void setSex(String sex) \{  
this.sex = sex;  
\}  
  
  
@Override  
public String toString() \{  
return "姓名："+this.name+",年龄："+this.age+",性别："+this.sex;  
\}  
  
  
@Override  
public int compareTo(User o) \{  
if(this.age>o.getAge())\{  
return 1;  
\}else\{  
return -1;  
\}  
\}  
  
  
\}

**test:**

package Test;  
  
  
import java.util.ArrayList;  
import java.util.Collections;  
import java.util.List;  
import java.util.Scanner;  
  
  
import org.junit.Test;  
  
  
public class TestUser \{  
@Test  
public void test1()\{  
List<User> list=new ArrayList<User>();  
Scanner sc=new Scanner(System.in);  
for(int i=0;i<3;i++)\{  
System.out.println("请输入姓名：");  
String name=sc.next();  
System.out.println("请输入年龄：");  
int age=sc.nextInt();  
System.out.println("请输入性别：");  
String sex=sc.next();  
User user=new User(name, age, sex);  
list.add(user);  
  
\}  
for(User user:list)\{  
System.out.println(user);  
\}  
System.out.println("\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*");  
System.out.println("排序后：");  
Collections.sort(list);  
for(User user:list)\{  
System.out.println(user);  
\}  
  
\}  
\}

**案例三：**

@Test  
public void test2()\{  
Map<String,Integer> ml=new HashMap<String,Integer>();  
ml.put("张三", 800);  
ml.put("李四", 1500);  
ml.put("王五", 3000);  
ml.put("张三", 2600);  
System.out.println(ml.get("张三"));  
System.out.println(ml.get("李四"));  
System.out.println(ml.get("王五"));  
System.out.println("\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#");  
  
Set<Entry<String, Integer>> entrySet=ml.entrySet();  
for(Entry<String, Integer> entry:entrySet)\{  
entry.setValue(entry.getValue()+100);  
System.out.println("姓名："+entry.getKey()); //获取Entry对象的key值  
System.out.println("工资："+entry.getValue()); //获取Entry对象的value值  
\}  
System.out.println("\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*");  
Set<String> ks = ml.keySet();  
for(String k : ks) \{  
System.out.println("姓名："+k);  
System.out.println("工资："+ml.get(k));  
\}  
  
  
\}

@Test  
public void test2sjb()\{  
Map<String,Integer> ml=new HashMap<String,Integer>();  
ml.put("张三", 800);  
ml.put("李四", 1500);  
ml.put("王五", 3000);  
print(ml);  
System.out.println("修改后");  
ml.put("张三", 2600);  
print(ml);  
  
System.out.println("加薪后1：");  
ml.put("张三",ml.get("张三")+100);  
ml.put("李四",ml.get("李四")+100);  
ml.put("王五",ml.get("王五")+100);  
print(ml);  
  
System.out.println("加薪后2");  
Set<Entry<String, Integer>> ens=ml.entrySet();  
for(Entry<String, Integer> entest:ens)\{  
int money=entest.getValue()+100;  
entest.setValue(money);  
\}  
print(ml);  
\}  
//1.  
private void print(Map<String,Integer> ml)\{  
Set<String> ks=ml.keySet();  
Iterator<String> itr=ks.iterator();  
while(itr.hasNext())\{  
String key=itr.next();  
int value=ml.get(key);  
System.out.println("key:"+key+"value:"+value);  
\}  
\}  
  
@Test  
public void test7()\{  
Employee zs=new Employee("张三", 800);  
Employee ls=new Employee("李四", 1500);  
Employee ww=new Employee("王五", 3000);  
Map<String,Employee> ep1=new HashMap<String, Employee>();  
ep1.put("张三", zs);  
Map<String,Employee> ep2=new HashMap<String, Employee>();  
ep2.put("李四", ls);  
Map<String,Employee> ep3=new HashMap<String, Employee>();  
ep3.put("王五", ww);  
List<Map<String,Employee>> list=new ArrayList<Map<String,Employee>>();  
list.add(ep1);  
list.add(ep2);  
list.add(ep3);  
for(Map<String, Employee> map:list)\{  
Set<Entry<String, Employee>> enset=map.entrySet();  
for(Entry<String, Employee> en:enset)\{  
//String key=en.getKey();  
Employee value = en.getValue();  
System.out.println("key:"+value.getName()+",value:"+value.getFee());  
\}  
\}  
\}  
/\*private void print(Map<String,Integer> ml)\{  
//3.  
Set<Entry<String, Integer>> entrySet = ml.entrySet();  
Iterator<Entry<String, Integer>> itr=entrySet.iterator();  
while(itr.hasNext())\{  
Entry<String, Integer> key=itr.next();  
System.out.println("key="+key.getKey()+"value="+key.getValue()); //获取Entry对象的key值  
//System.out.println("value="+key.getValue()); //获取Entry对象的value值  
\}  
  
//2.  
Set<Entry<String, Integer>> entrySet = ml.entrySet();  
for(Entry<String, Integer> en : entrySet) \{  
System.out.println("key="+en.getKey()); //获取Entry对象的key值  
System.out.println("value="+en.getValue()); //获取Entry对象的value值  
\}  
  
\}\*/

**案例四：**

Car:

package Map;  
  
  
public class Car \{  
private String name;  
private int speed;  
  
public Car(String name, int speed) \{  
this.name = name;  
this.speed = speed;  
\}  
  
  
public String getName() \{  
return name;  
\}  
  
  
public void setName(String name) \{  
this.name = name;  
\}  
  
  
public int getSpeed() \{  
return speed;  
\}  
  
  
public void setSpeed(int speed) \{  
this.speed = speed;  
\}  
  
  
\}

test:

@Test  
public void test3sjb()\{  
Car c1=new Car("奥拓", 100);  
Car c2=new Car("宝马", 200);  
Car c3=new Car("奔驰", 300);  
Map<Car,Integer> ml=new HashMap<Car, Integer>();  
ml.put(c1, 10000);  
ml.put(c2, 500000);  
ml.put(c3, 2000000);  
Set<Entry<Car, Integer>> entry1=ml.entrySet();  
for(Entry<Car, Integer> en1:entry1)\{  
Car val = en1.getKey();  
System.out.println(val.getName());  
  
if(val.getName().equals("宝马"))\{  
System.out.println("“宝马”的价格"+en1.getValue());  
\}  
\}  
for(Entry<Car, Integer> en2:entry1)\{  
double price=en2.getValue()\*0.8;  
System.out.println("品牌："+en2.getKey().getName()+",价格为："+price);  
\}  
\}

**practice:1-6**

@Test  
public void test1()\{  
List i=new ArrayList();  
i.add("abc");  
i.add(true);  
i.add(1);  
System.out.println(i.size());//获取集合中元素的个数  
System.out.println(i.get(0));//获取集合中的元素，索引值从0开始  
i.remove("abc"); //删除集合中的元素  
i.remove(0);//删除集合中的元素，索引从0开始  
i.clear(); //删除集合中所有元素  
System.out.println(i.contains("abc"));  
\}  
  
@Test  
public void test2()\{  
Set<Integer> set=new HashSet<Integer>();  
set.add(1);  
set.add(4);  
set.add(3);  
System.out.println(set.size());  
/\*Iterator<Integer> itr=set.iterator();  
while(itr.hasNext())\{  
Integer i = itr.next();  
System.out.println(i);  
\}\*/  
\}  
@Test  
public void test3()\{  
Set<Integer> set=new HashSet<Integer>();  
while(true)\{  
int x=(int)(Math.random()\*10);  
System.out.println(x);  
if(set.size()<5)\{  
set.add(x);  
\}else\{  
break;  
\}  
\}  
System.out.println(set.toString());  
\}  
@Test  
public void test4()\{  
Map<String,String> map=new HashMap<String, String>();  
map.put("no1", "bj");  
map.put("no2", "sh");  
map.put("no3", "gz");  
map.put("no4", null);  
map.put(null, "bj");  
System.out.println(map.get("no1"));  
Set<String> set=map.keySet();  
Iterator<String> ks=set.iterator();  
while(ks.hasNext())\{  
String key = ks.next();  
String value = map.get(key);  
System.out.println(key+value);  
\}  
System.out.println("\#\#\#\#\#\#\#\#\#\#\#");  
for(String key:set)\{//Set<String> set=map.keySet();  
String value=map.get(key);  
System.out.println(key+value);  
\}  
\}  
  
@Test  
public void test5()\{  
Map<String,String> map=new HashMap<String, String>();  
map.put("no1", "bj");  
map.put("no2", "sh");  
map.put("no3", "gz");  
map.put("no4", null);  
map.put(null, "bj");  
Set<Entry<String, String>> set=map.entrySet();  
Iterator<Entry<String, String>> ks=set.iterator();  
while(ks.hasNext())\{  
Entry<String, String> ey = ks.next();  
String key = ey.getKey();  
String value = ey.getValue();  
System.out.println(key+value);  
\}  
System.out.println("\*\*\*\*\*\*\*\*\*\*");  
for(Entry<String, String> en:set)\{//Set<Entry<String, String>> set=map.entrySet();  
System.out.println(en.getKey()+en.getValue());  
\}  
\}  
@Test  
public void test6()\{  
List<Integer> list=new ArrayList<Integer>();  
list.add(7);  
list.add(45);  
list.add(23);  
list.add(78);  
System.out.println(list.toString());  
Collections.sort(list);  
System.out.println(list.toString());  
System.out.println(Collections.max(list));  
System.out.println(Collections.min(list));  
Collections.replaceAll(list, 45, 888);  
System.out.println(list.toString());  
\}  
  
\}

@Test  
public void test5() \{  
List<News> news = new ArrayList<News>();  
News news1 = new News("中国多地遭雾霾笼罩空气质量再成热议话题");  
News news2 = new News("春节临近北京“卖房热”");  
news.add(news1);  
news.add(news2);  
  
Iterator<News> itr = news.iterator();  
  
while(itr.hasNext()) \{  
News totlenews = itr.next();  
String title = totlenews.getTitle();  
if(title.length() >= 15) \{  
title = title.substring(0, 14)+"...";  
\}  
totlenews.setTitle(title);  
System.out.println(totlenews);  
\}  
\}