黑马程序员 Java 电子版 pdf 黑马程序员java课件

目录

1、泛型

        1、泛型的定义格式：

        1.1 泛型的好处：

         2、泛型类：

        3、泛型方法：

        4、泛型接口：

        5、类型通配符：

        6、可变参数：

         7、可变参数的使用：

 2、Map集合

        1、Map集合的概述和特点

         2、Map集合的基本功能

         3、Map集合的获取功能

        4、Map集合的遍历

        4.1遍历方法一

        4.2遍历方法二

        5、HashMap集合案例

        5.1案例一

        5.2案例二

        6、集合嵌套

        6.1集合嵌套之ArrayList嵌套HashMap

        6.2集合嵌套之HashMap嵌套ArrayList

        7、统计字符串每个字符出现的次数

         8、Collections的概述和使用

         9、用ArrayList集合存储学生并遍历

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1、泛型

        1、泛型的定义格式：

        1.1 泛型的好处：

 2、泛型类：

        //泛型类

//泛型类
public class Generic<T>{
    private T t;

    public T getT(){
        return t;
    }
    public void setT(T t){
        this.t =t;
    }
}

//测试类

//测试类
public class work11{
    public static void main(String[] args){
        Student s = new Student();
        Generic<String> g = new Generic<>();
        g.setT("中国");
        System.out.println(g.getT());          //中国
        System.out.println("----------");
        Generic<Integer> g1 = new Generic<>();
        g1.setT(100);
        System.out.println(g1.getT());         //100
        System.out.println("----------");
        Generic<Boolean> g2 = new Generic<>();
        g2.setT(true);
        System.out.println(g2.getT());         //true
    }
}

3、泛型方法：

        //Generic类中定义泛型方法

//Generic类
public class Generic{
    public <T> void show(T t){
        System.out.println(t);
    }
}

//测试类

public class work11{
    public static void main(String[] args){
        Generic g = new Generic();
        g.show("中国");         //中国
        g.show(100);           //100
        g.show(true);          //true
        g.show(12.34);         //12.34
    }
}

4、泛型接口：

        //接口

public interface Generic<T>{
    void show(T t);
}

//实现接口的类

public class GenericImpl<T> implements Generic<T>{
    @Override
    public void show(T t) {
        System.out.println(t);
    }
}

//测试类

public class work11{
    public static void main(String[] args){
        Generic<String> g = new GenericImpl<>();
        g.show("中国");                   //中国
        Generic<Integer> g2 = new GenericImpl<>();
        g2.show(100);                    //100
        Generic<Boolean> g3 = new GenericImpl<>();
        g3.show(true);                   //true
    }
}

5、类型通配符：

import java.util.*;

public class work11{
    public static void main(String[] args){
        List<?> list1 = new ArrayList<Object>();
        List<?> list2 = new ArrayList<Number>();
        List<?> list3 = new ArrayList<Integer>();
        System.out.println("-----------");
        //List<? extends Number> list4 = new ArrayList<Object>();     会报错
        List<? extends Number> list4 = new ArrayList<Number>();
        List<? extends Number> list5 = new ArrayList<Integer>();
        System.out.println("-----------");
        //List<? super Number> list6 = new ArrayList<Integer>();      会报错
        List<? super Number> list6 = new ArrayList<Object>();
        List<? super Number> list7 = new ArrayList<Number>();
    }
}

6、可变参数：

public class work11{
    public static void main(String[] args){
        System.out.println(sum(10,20));                  //30
        System.out.println(sum(10,20,30));               //60
        System.out.println(sum(10,20,30,40));            //100
        System.out.println(sum(10,20,30,40,50));         //150
        System.out.println(sum(10,20,30,40,50,60));      //210
    }
    /*
        public static int sum(int b,int...a){
            int sum = b;
            for(int i:a){
                sum += i;
            }
            return sum;
        }
     */
    public static int sum(int...a){
        int sum = 0;
        for(int i:a){
            sum += i;
        }
        return sum;
    }
}

 7、可变参数的使用：

import java.util.*;

public class work11{
    public static void main(String[] args){
        List<String> list1 = Arrays.asList("hello","world","java");
//        list1.add("javaee");         //会报错
//        list1.remove("hello");       //会报错
        list1.set(1,"javaee");
        System.out.println(list1);     //[hello, javaee, java]
        System.out.println("------------");
        List<String> list2 = List.of("hello","world","java");
//        list1.add("javaee");         //会报错
//        list1.remove("hello");       //会报错
//        list1.set(1,"javaee");       //会报错
        System.out.println(list2);     //[hello, world, java]
        System.out.println("------------");
        Set<String> set = Set.of("hello","world","java");
//        Set<String> set = Set.of("hello","world","java","hello");  //会报错
//        list1.add("javaee");         //会报错
//        list1.remove("hello");       //会报错
//        list1.set(1,"javaee");       //会报错
        System.out.println(set);       //[world, java, hello]
    }
}

 2、Map集合

        1、Map集合的概述和特点

import java.util.*;

public class work11{
    public static void main(String[] args){
        Map<Integer,String> map = new HashMap<>();
        //put方法，键不存在时为添加，如果键存在时为修改
        map.put(1,"风清扬");
        map.put(2,"天山果佬");
        map.put(3,"橙留香");
        map.put(3,"菠萝吹雪");
        System.out.println(map);    //{1=风清扬, 2=天山果佬, 3=菠萝吹雪}
    }
}

         2、Map集合的基本功能

import java.util.*;

public class work11{
    public static void main(String[] args){
        //创建Map对象
        Map<Integer,String> map = new HashMap<>();
        //put方法，键值不存在时为添加，如果键值存在时为修改
        map.put(1,"风清扬");
        map.put(2,"天山果佬");
        map.put(3,"菠萝吹雪");
        System.out.println(map);    //{1=风清扬, 2=天山果佬, 3=菠萝吹雪}

        System.out.println(map.remove(1));     //风清扬
        System.out.println(map.remove(1));     //null
        System.out.println(map);    //{2=天山果佬, 3=菠萝吹雪}

        System.out.println(map.containsKey(2));   //true
        System.out.println(map.containsValue("菠萝吹雪"));  //true

        System.out.println(map.size());     //2

        map.clear();       //移除Map集合中的所有键值对
        System.out.println(map.isEmpty());   //true
    }
}

3、Map集合的获取功能

import java.util.*;

public class work11{
    public static void main(String[] args){
        //创建Map对象
        Map<Integer,String> map = new HashMap<>();
        //put方法，键值不存在时为添加，如果键值存在时为修改
        map.put(1,"风清扬");
        map.put(2,"天山果佬");
        map.put(3,"菠萝吹雪");

        System.out.println(map.get(1));  //风清扬
        System.out.println(map.get(4));  //null

        Set<Integer> set = map.keySet();
        for(Integer i:set){
            System.out.println(i);       //1 2 3
        }

        Collection<String> c = map.values();
        for(String s:c){
            System.out.println(s);      //风清扬 天山果佬 菠萝吹雪
        }
    }
}

        4、Map集合的遍历

        4.1遍历方法一

import java.util.*;

public class work11{
    public static void main(String[] args){
        //创建Map对象
        Map<Integer,String> map = new HashMap<>();
        //put方法，键值不存在时为添加，如果键值存在时为修改
        map.put(1,"风清扬");
        map.put(2,"天山果佬");
        map.put(3,"菠萝吹雪");
        //获取键的集合
        Set<Integer> set = map.keySet();
        //用加强for循环遍历
        for(Integer i:set){
            //根据键获取相应的值
            String s = map.get(i);
            System.out.println(i+","+s);
        }
    }
}

4.2遍历方法二

import java.util.*;

public class work11{
    public static void main(String[] args){
        //创建Map对象
        Map<Integer,String> map = new HashMap<>();
        //put方法，键值不存在时为添加，如果键值存在时为修改
        map.put(1,"风清扬");
        map.put(2,"天山果佬");
        map.put(3,"菠萝吹雪");
        //获取键值对的集合
        Set<Map.Entry<Integer,String>> entrySet = map.entrySet();
        //用加强for循环遍历
        for(Map.Entry<Integer,String> me:entrySet){
            int i = me.getKey();
            String s = me.getValue();
            System.out.println(i+","+s);
        }
    }
}

5、HashMap集合案例

        5.1案例一

//测试类
import java.util.*;

public class work11{
    public static void main(String[] args){
        //创建HashMap集合
        HashMap<String,Student> hm = new HashMap<>();
        //创建学生对象
        Student s1 = new Student("风清扬",30);
        Student s2 = new Student("天山果佬",35);
        Student s3 = new Student("菠萝吹雪",33);
        hm.put("itheima001",s1);
        hm.put("itheima002",s2);
        hm.put("itheima003",s3);
        //创建所有键的集合
        Set<String> set = hm.keySet();
        //用加强for循环遍历
        for(String s:set){
            Student ss = hm.get(s);
            System.out.println(s+","+ss.getName()+","+ss.getAge());
        }
        System.out.println("----------");
        //创建所有键值对的集合
        Set<Map.Entry<String,Student>> entrySet = hm.entrySet();
        //用加强for循环遍历
        for(Map.Entry<String,Student> me:entrySet){
            String s = me.getKey();
            Student ss = me.getValue();
            System.out.println(s+","+ss.getName()+","+ss.getAge());
        }
    }
}

//学生类
public class Student{
    private String name;
    private int age;

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

    public void setName(String name){
        this.name = name;
    }
    public String getName(){
        return name;
    }

    public void setAge(int age){
        this.age = age;
    }
    public int getAge(){
        return age;
    }
}

        5.2案例二

//测试类
import java.util.*;

public class work11{
    public static void main(String[] args){
        //创建HashMap集合
        HashMap<Student,String> hm = new HashMap<>();
        //创建学生对象
        Student s1 = new Student("风清扬",30);
        Student s2 = new Student("天山果佬",35);
        Student s3 = new Student("菠萝吹雪",33);
        hm.put(s1,"itheima001");
        hm.put(s2,"itheima002");
        hm.put(s3,"itheima003");
        //创建所有键的集合
        Set<Student> set = hm.keySet();
        //用加强for循环遍历
        for(Student s:set){
            String ss = hm.get(s);
            System.out.println(ss+","+s.getName()+","+s.getAge());
        }
        System.out.println("----------");
        //创建所有键值对的集合
        Set<Map.Entry<Student,String>> entrySet = hm.entrySet();
        //用加强for循环遍历
        for(Map.Entry<Student,String> me:entrySet){
            Student s = me.getKey();
            String ss = me.getValue();
            System.out.println(ss+","+s.getName()+","+s.getAge());
        }
    }
}

//学生类
public class Student{
    private String name;
    private int age;

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

    public void setName(String name){
        this.name = name;
    }
    public String getName(){
        return name;
    }

    public void setAge(int age){
        this.age = age;
    }
    public int getAge(){
        return age;
    }
}

6、集合嵌套

        6.1集合嵌套之ArrayList嵌套HashMap

import java.util.*;

public class work11{
    public static void main(String[] args){
        ArrayList<HashMap<String,String>> array = new ArrayList<>();
        HashMap<String,String> hm1 = new HashMap<>();
        hm1.put("杨过","小龙女");
        hm1.put("郭靖","黄蓉");
        array.add(hm1);

        HashMap<String,String> hm2 = new HashMap<>();
        hm2.put("孙策","大乔");
        hm2.put("周瑜","小乔");
        array.add(hm2);

        HashMap<String,String> hm3 = new HashMap<>();
        hm3.put("李白","王昭君");
        hm3.put("干将","莫邪");
        array.add(hm3);

        for(HashMap<String,String> me:array){
            Set<String> set = me.keySet();
            for(String s:set){
                String ss = me.get(s);
                System.out.println(ss+","+s);
            }
            System.out.println("----------");
        }
        System.out.println("遍历的另一种方法：");
        for(HashMap<String,String> me:array){
            Set<Map.Entry<String,String>> entrySet = me.entrySet();
            for(Map.Entry<String,String> mo:entrySet){
                String s = mo.getKey();
                String ss = mo.getValue();
                System.out.println(s+","+ss);
            }
            System.out.println("----------");
        }
    }
}

结果： 

 

 

        6.2集合嵌套之HashMap嵌套ArrayList

import java.util.*;

public class work {
    public static void main(String[] args){
        HashMap<String,ArrayList<String>> map = new HashMap<>();

        ArrayList<String> array1 = new ArrayList<>();
        array1.add("橙留香");
        array1.add("菠萝吹雪");
        map.put("果宝特攻",array1);

        ArrayList<String> array2 = new ArrayList<>();
        array2.add("杨过");
        array2.add("小龙女");
        map.put("神雕侠侣",array2);

        Set<Map.Entry<String,ArrayList<String>>> entrySet = map.entrySet();
        for(Map.Entry<String,ArrayList<String>> me:entrySet){
            String s = me.getKey();
            ArrayList<String> list = me.getValue();
            System.out.println(s);
            for(String ss:list){
                System.out.println("\t" + ss);
            }
        }
        System.out.println("以下是另一种方法：");
        Set<String> set = map.keySet();
        for(String s:set){
            ArrayList<String> list = map.get(s);
            System.out.println(s);
            for(String ss:list){
                System.out.println("\t" + ss);
            }
        }
    }
}

 结果： 

 

 

7、统计字符串每个字符出现的次数

import java.util.*;

public class work {
    public static void main(String[] args){
        //从键盘录入一个字符串
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入字符串");
        String line = sc.nextLine();
        //创建HashMap集合
       HashMap<Character,Integer> hm = new HashMap<>();

        //如果要按键的顺序打印在控制面板上，使用TreeMap
        //TreeMap<Character,Integer> hm = new TreeMap<>();

        //遍历字符串，得到没一个字符
        for(int i=0;i<line.length();i++){
            char c = line.charAt(i);
            //用字符键来寻找对应的值
            Integer x = hm.get(c);
            //如果返回null，说明该字符在集合中不存在，将该字符作为键，1作为值存储
            if(x == null){
                hm.put(c,1);
            //返回的不是null，说明该字符已经存在，将该字符对应的值加1在进行存储
            }else {
                x++;
                hm.put(c,x);
            }
        }
        //创建一个StringBuilder对象，按要求进行拼接
        StringBuilder sb = new StringBuilder();
        //遍历HashMap集合
        Set<Character> set = hm.keySet();
        for(Character y:set){
            Integer i = hm.get(y);
            //按要求拼接
            sb.append(y).append("(").append(i).append(")");
        }
        String ss = sb.toString();
        System.out.println(ss);
    }
}

   结果：

         8、Collections的概述和使用

import java.util.*;

public class work{
    public static void main(String[] args){
        ArrayList<String> arrayList = new ArrayList<>();
        arrayList.add("风清扬");
        arrayList.add("林青霞");
        arrayList.add("橙留香");
        arrayList.add("菠萝吹雪");

        //sort方法排序
        Collections.sort(arrayList);
        System.out.println(arrayList);

        //reverse方法倒叙
        Collections.reverse(arrayList);
        System.out.println(arrayList);

        //shuffle方法随机排序
        Collections.shuffle(arrayList);
        System.out.println(arrayList);

    }
}

结果：

9、用ArrayList集合存储学生并遍历

//测试类
import java.util.*;

public class work{
    public static void main(String[] args){
        ArrayList<Student> list = new ArrayList<Student>();
        list.add(new Student("林青霞",30));
        list.add(new Student("风清扬",33));
        list.add(new Student("橙留香",10));
        Collections.sort(list, new Comparator<Student>() {
            @Override
            public int compare(Student o1, Student o2) {
                int num1 = o1.getAge() - o2.getAge();
                int num2 = num1 == 0? o1.getName().compareTo(o2.getName()):num1;
                return num2;
            }
        });
        for(Student s:list){
            System.out.println(s.getName()+","+s.getAge());
        }
    }
}

//学生类
public class Student {
    private String name;
    private int age;

    public Student() {
    }

    public Student(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;
    }
}

 结果：