java基础第18课

work092.java

package test05;


import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;


public class work092
{


  public static void main(String[] args)
  {
    List<String> list1 = new ArrayList<>();  //元素可重复
    list1.add("a");
    list1.add("b");
    list1.add("c");
    list1.add("d");
    list1.add("a");
    list1.add("b");
    list1.add("c");
    list1.add("d");
    int i = (int)(Math.random() * list1.size());
    System.out.println("随机获取数组中的元素：" + list1.get(i));
    list1.remove(2);
    System.out.println("移除索引为2后，数组中的元素：");
    for (int j = 0; j < list1.size(); j++)
    {
      System.out.print(list1.get(j) + " ");
    }
    System.out.println();

    List<String> list2 = new LinkedList<>(); //元素可重复
    list2.add("aa");
    list2.add("bb");
    list2.add("cc");
    list2.add("dd");
    list2.add("aa");
    list2.add("bb");
    list2.add("cc");
    list2.add("dd");
    int index = (int)(Math.random() * list2.size());
    System.out.println("随机获取数组中的元素：" + list2.get(index));
    list2.remove(1);
    System.out.println("移除索引1后，数组中元素为：");
    for (int j = 0; j < list2.size(); j++)
    {
      System.out.print(list2.get(j) + " ");
    }


  }


}

work093.java

package test05;


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


public class work093 implements Comparable<Object>
{
private String name;
private long id;

public work093(String name,long id)
{
this.name = name;
this.id = id;
  }

public int compareTo(Object obj)
{
work093 stu1 = (work093)obj;
int result;
if (this.id > stu1.id)
    {
result = 1;
    }
else if (this.id == stu1.id)
    {
result = 0;
    }
else 
    {
result= -1;
    }  
return result;
  }

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

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

public long getId()
{
return this.id;
  }

public void setId(long id)
{
this.id = id;
  }

public static void main(String[] args)
{
work093 stu1 = new work093("张龙", 01011); //八进制数
work093 stu2 = new work093("赵虎", 01021);
work093 stu3 = new work093("王朝", 01051);
work093 stu4 = new work093("马汉", 01012);

TreeSet<work093> tree1 = new TreeSet<>();
tree1.add(stu1);
tree1.add(stu2);
tree1.add(stu3);
tree1.add(stu4);
Iterator<work093> iterator1 = tree1.iterator();
System.out.println("set集合中的所有元素:");
while (iterator1.hasNext())
    {
work093 temp = (work093) iterator1.next();
System.out.println("id:" + temp.getId() + " name:" + temp.getName());

    }


iterator1 = tree1.headSet(stu2).iterator(); //截取排在stu2之前的集合
System.out.println("截取前面部分的集合：");
while (iterator1.hasNext())
    {
work093 temp = (work093) iterator1.next();
System.out.println("id:" + temp.getId() + " name:" + temp.getName());
    }

iterator1 = tree1.subSet(stu2, stu3).iterator();
System.out.println("截取中间部分的集合：");
while (iterator1.hasNext())
    {
work093 temp = (work093) iterator1.next();
System.out.println("id:" + temp.getId() + " name:" + temp.getName());
    }


  }


}