java基础知识之五：（list循环、排序、数组与list转化）

package com.sd.Lista;import java.util.*;/** * Created by ztf on 2017-5-24. * java集合的主要分为三种类型：set（集）、List（列表)、Map(映射) */public class ListTest {    public static void main(String[] args) {        List<String> list = new ArrayList<String>();        list.add("张三");        list.add("李四");        list.add("王五");        list.add("历史");       //升序        Collections.sort(list);        //list循环的方式一        for(String str:list){            System.out.println("list循环方式一="+str);        }        //降序        Collections.reverse(list);        //list循环的方式二        Iterator  iterator = list.iterator();        while (iterator.hasNext()){            System.out.println("list循环方式二="+iterator.next());        }        //list循环的方式三        for(Iterator it3=list.iterator();it3.hasNext();){            System.out.println("list循环方式三="+it3.next());        }        //list循环的方式三        for(int i = 0;i < list.size(); i ++){            System.out.println("list循环方式四="+list.get(i));        }       //list转数组        int size=list.size();        String[] array = (String[])list.toArray(new String[list.size()]);      //  String[] array = (String[])list.toArray(new String[size]);        for(int i=0;i<array.length;i++){            System.out.println(array[i]);        }        //数组转list        List<String> list1 = Arrays.asList(array);        for(int i = 0;i < list1.size(); i ++){            System.out.println("转化后="+list1.get(i));        }        //字符串转数组，数组转List        String str = "121,12,2,ads,aqe,qwq";        String[] arrrayss = str.split(",");        List<String> list2 = Arrays.asList(arrrayss);        String[] strs = (String[])list2.toArray(new String[list2.size()]);        for(String ss:strs){            System.out.println("arrray数组="+ss);        }        for(String ss:list2){            System.out.println("字符串转化的list="+ss);        }        Map<String,Integer> map = new HashMap<String,Integer>();        map.put("aa",1);        map.put("bb",2);        map.put("cc",3);        map.put("dd",4);        //map循环方式一        for(Map.Entry<String,Integer> entry:map.entrySet()){            System.out.println("testKey = " + entry.getKey() + ", testValue = " + entry.getValue());        }        for(String key:map.keySet()){            System.out.println("Key = " + key +"&&value="+map.get(key));        }        for(Integer value:map.values()){            System.out.println("value = " + value);        }        //map第二种循环方式        Iterator<Map.Entry<String, Integer>> entries = map.entrySet().iterator();        while (entries.hasNext()) {            Map.Entry<String, Integer> entry = entries.next();            System.out.println("Key = " + entry.getKey() + ",asdas Value = " + entry.getValue());        }//        //位运算符//        int a = 1;//        int b = a>>1;//        System.out.println("sadffa="+b);    }}

package com.sd.Lista;/** * Created by ztf on 2017-5-25. */public class Student implements Comparable{    public Student(String name,Integer age){        this.name = name;        this.age = age;    }    private String name;    private Integer age;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Integer getAge() {        return age;    }    public void setAge(Integer age) {        this.age = age;    }    @Override    public int compareTo(Object o) {        Student ss = (Student)o;        return this.age.compareTo(ss.getAge());    }}

package com.sd.Lista;/** * Created by ztf on 2017-5-25. */public class Teacher {    private String name;    private Integer age;    public Teacher(String name,Integer age){        this.name = name;        this.age = age;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Integer getAge() {        return age;    }    public void setAge(Integer age) {        this.age = age;    }}

package com.sd.Lista;

import java.util.*;

/**
* Created by ztf on 2017-5-25.
*/
public class ListSortTest implements Comparator{

public static void main(String[] args) {    Student ss1 = new Student("张三",10);    Student ss2 = new Student("李四",33);    Student ss3 = new Student("王五",23);    List<Student> st = new ArrayList<Student>();    st.add(ss1);    st.add(ss2);    st.add(ss3);    //升序    Collections.sort(st);    for (Student ss:st){        System.out.println("学生姓名："+ss.getName()+"年龄："+ss.getAge());    }    //降序    Collections.reverse(st);    for (Student ss:st){        System.out.println("学生姓名："+ss.getName()+"年龄："+ss.getAge());    }    Teacher tt1 = new Teacher("王老师",33);    Teacher tt2 = new Teacher("李老师",44);    Teacher tt3 = new Teacher("dai老师",40);    List<Teacher> listTeacher = new ArrayList<>();    listTeacher.add(tt1);    listTeacher.add(tt2);    listTeacher.add(tt3);    Collections.sort(listTeacher,new ListSortTest());    for (Teacher ss:listTeacher){        System.out.println("老师姓名："+ss.getName()+"老师年龄："+ss.getAge());    }    Collections.reverse(listTeacher);    for (Teacher ss:listTeacher){        System.out.println("老师姓名："+ss.getName()+"老师年龄："+ss.getAge());    }}@Overridepublic int compare(Object o1, Object o2) {    Teacher teacher1 = (Teacher)o1;    Teacher teacher2 = (Teacher)o2;    return teacher1.getAge().compareTo(teacher2.getAge());}

}