运用新的软件开发。IDEA.复盘内容三。

运用新的软件开发。IDEA.复盘内容三。

 上面是今天所要学习的内容模块。

---

@1回顾集合Arraylist.

 运行结果

package Collection1;

import java.util.ArrayList;

public class ArrayListDemo1 {
	public static void main(String[] args) {
		ArrayList list =new   ArrayList();
		
		list.add(56);
		list.add(10);
		list.add(58);
		list.add(890);
		list.add(786);
		list.add(89);
		list.add(565);
		list.add(678);
		//list.add(" l love you ");
		list.add(90);
		list.add(78);
		
		list.remove(2);
		list.remove(new Integer(58));
		//删除指定内容元素
		//list.remove(" l love you");
		list.remove(1);
		System.out.println(list.size());
		//修改
		list.set(2, 1);
		
		//查询数据
		Object obj =list.get(0);
		System.out.println(list.get(0));
		list.get(2);
		System.out.println(list.get(2));
		System.out.println(list);
		for (int i = 0; i < list.size(); i++) {
			System.out.println(list.get(i));
			
		}
		
		
		
	}

}

---

@2程序异常的一些常看到的错误。

 

来了解一下吧.

 第一种错误： java.lang.ArithmeticException: / by zero
    at ExceptionDemo2.ExceptionDemo1.main(ExceptionDemo1.java:8)

第二种错误。 java.lang.NumberFormatException: For input string: "abd"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:580)
    at java.lang.Integer.(Integer.java:867)
    at ExceptionDemo2.ExceptionDemo2.main(ExceptionDemo2.java:7)

第三种错误。java.lang.NumberFormatException: For input string: "abd"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:580)
    at java.lang.Integer.(Integer.java:867)
    at ExceptionDemo2.ExceptionDemo3.main(ExceptionDemo3.java:34)

---

第四种错误。

java.lang.ArrayIndexOutOfBoundsException: 3
    at Throw.ThorowDemo1.method1(ThorowDemo1.java:35)
    at Throw.ThorowDemo1.main(ThorowDemo1.java:14) 代码内容。

package Throw;

import java.text.ParseException;

import java.text.SimpleDateFormat;
import java.util.Date;

public class ThorowDemo1 {

	public static void main(String[] args) {
		System.out.println("程序开始");
		method();
		try {
			method1();
		}catch(ArrayIndexOutOfBoundsException  e) {
			e.printStackTrace();
		}
		
		
		System.out.println("程序结束了哦哦哦");
	}
		public static void method() {
			String s ="2021-05-01";
			SimpleDateFormat sdf=new SimpleDateFormat("yyyy-mm-dd");
			try {
			Date date = sdf.parse(s);
			}catch(ParseException r) {
				r.printStackTrace();	
			}
			
		}
//谁调用就跟谁
		public static void method1() throws ArrayIndexOutOfBoundsException{
			int [] arr =new int [3];
			System.out.println(arr[3]);
			
		}
	}

 

@3Collection的集合内容.

package collection;


import java.util.*;
public class CollectionDemo2 {

	
	public static void main(String[] args) {
		//创建一个集合对象
		Collection c = new ArrayList();
		
		//创建3个学生对象
		Student s1 = new Student("刘德华",55);
		Student s2 = new Student("张学友",58);
		Student s3 = new Student("黎明",52);
		Student s4 =new Student("自学",23);
		Student s5 =new Student("限为",203);
		
		//将3个学生对象添加到集合当中
		c.add(s1);
		c.add(s2);
		c.add(s3);
		c.add(s4);
		c.add(s5);
		System.out.println("采用迭代器遍历集合的元素");
		//采用迭代器遍历集合的元素
		Iterator it = c.iterator();
		while(it.hasNext()){
			Student s = it.next();
			System.out.println("学生的姓名："+s.getName()+",学生的年龄："+s.getAge());
		}
	}

}

---

---

@4for循环遍历的三中方式.

package for1;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import list.Student;

public class Forday {

	public static void main(String[] args) {
		int [] arr = {12,34,56,7,78,9233,33333};
		//第一种方法
		for (int i = 0; i < arr.length; i++) {
			System.out.println(arr[i]);
			
		}
		System.out.println("----------------------------");
		//第二种方法
		//for(数据类型 变量名:集合/数组){System.out.println();}
		for(int a:arr) {
			System.out.println(a);
		}
		System.out.println("============================================================================================");
		//2
		List  c =new ArrayList ();
		//创建一个list的集合对象
		Student s1 =new Student("小额",23);
		Student s2 =new Student("小王",73);
		Student s3 =new Student("小红",103);
		Student s4 =new Student("小q",23);
		Student s5 =new Student("小",33);
		
		c.add(s1);
		c.add(s2);
		c.add(s3);
		c.add(s4);
		c.add(s5);
		
		//第一种方法
		System.out.println("11111111111111111111111111111111");
		Iterator  it =c.iterator();
		while(it.hasNext()) {
			Student s=it.next();
			System.out.println("学生姓名:"+s.getName()+",学生年龄:"+s.getAge());
		}
		System.out.println("===============222222222222222222=========================================");
		//第二种方法
		for (Student student : c) {
			System.out.println(student);
			
		}
	
		System.out.println("===================3333333333333===========================================");
		//第三种方式
		for (int j = 0; j < c.size(); j++) {
			System.out.println(c);
			
		}
		}
	}

@5linkedList集合。

package linkedList;

import java.util.linkedList;
import java.util.List;

public class linkedListTest{  
	  

	public static  void main(String[] args) {  
	    linkedList lList = new linkedList();  
	    lList.add("stu");  
	    lList.add("stu1");  
	    lList.add("stu2");  
	    lList.add("stu3");  
	    lList.add("stu4");  
	    lList.add("stu5");  
	    lList.add("stu6");  
	    lList.add("stu7");  
	    lList.add("stu8");  
	    lList.add("stu9"); 
	   
	  
	    System.out.println("链表的第一个元素是 : " + lList.getFirst());  
	    System.out.println("链表最后一个元素是 : " + lList.getLast());  
	  
	    
	    for (String str: lList) {  
	        System.out.println(str);  
	      }  
	  
	    
		  
	    List subl = lList.subList(1, 6);  
	    System.out.println(subl);  
	    lList.remove(2);  
	    System.out.println(lList);  
	    System.out.println(lList); 
	  }  
	}  

@6Set的集合

package Setday;

import java.util.HashSet;
import java.util.Set;

public class Setday {

	private static char[] str;

	public static void main(String[] args) {
		Set s=new HashSet();
		s.add("a");
		s.add("ab");
		s.add("abc");
		s.add("abcd");
		for (String string : s) {
			System.out.println(s);
		}
		
		System.out.println("------------------------------------");
		for (int i = 0; i < s.size(); i++) {
			System.out.println(s);
			
		}
		

	}

}

@8List

import java.util.ArrayList;
import java.util.Iterator;
import java.util.Set;
import java.util.TreeSet;

public class List {

	public static void main(String[] args) {
		//list集合遍历
		ArrayList   list=new ArrayList();
		list.add("heiiow  嗯嗯word do you");
		list.add("heiiow like 好了do you");
		list.add("hei口口iow love do you");
		list.add("heiiow mayn买空卖空t do you");
		list.add("heiiow ma黄金国际p do you");
		list.add("hei浏览器登录iow list do you");
		//第一种遍历
		for (int i = 0; i < list.size(); i++) {
			System.out.println(list.get(i));
			
		}
		System.out.println("-------------1111------------------");
		//第二种遍历
		Iterator it =list.iterator();
		while(it.hasNext()) {
			System.out.println(it.next());
			
		}
		System.out.println("==========2222====================");
		//第三种
		for (String l : list) {
			System.out.println(l);
		}
		System.out.println("===========33333====================");
		System.out.println("-------------------------------");
		//第四种
		for (Object Object: list) {
			System.out.println(Object);
				}
		
			
		}
		
	}

 上面的错误如何解决。代码如下。

package com.chengji.paixun;

import java.util.TreeSet;

public class StudentTest01 {

	
	 public static void main(String[] args) {
	        //创建TreeSet集合对象，通过比较器排序进行排序
		  TreeSet ts = new TreeSet();
		  
		  //创建学生对象
	        Student s1 = new Student("林青霞", 98, 100);
	        Student s2 = new Student("张曼玉", 95, 95);
	        Student s3 = new Student("王祖贤", 100, 93);
	        Student s4 = new Student("柳岩", 100, 97);
	        Student s5 = new Student("风清扬", 98, 98);

	        Student s6 = new Student("左冷禅", 97, 99);
//	        Student s7 = new Student("左冷禅", 97, 99);
	        Student s7 = new Student("赵云", 97, 99);

	        //把学生对象添加到集合
	        ts.add(s1);
	        ts.add(s2);
	        ts.add(s3);
	        ts.add(s4);
	        ts.add(s5);
	        ts.add(s6);
	        ts.add(s7);
	        
	        
	     

	        //遍历集合
	        for (Student s : ts) {
	            System.out.println(s.getName() + "," + s.getChinese() + "," + s.getMath() + "," + s.getSum());
	        }
	 }
		  
}

package com.chengji.paixun;

public class Student {
	 private String name;
	    private int chinese;
	    private int math;

	    public Student() {
	    }

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

	    public String getName() {
	        return name;
	    }

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

	    public int getChinese() {
	        return chinese;
	    }

	    public void setChinese(int chinese) {
	        this.chinese = chinese;
	    }

	    public int getMath() {
	        return math;
	    }

	    public void setMath(int math) {
	        this.math = math;
	    }

	    public int getSum() {
	        return this.chinese + this.math;
	        

		
		}
	    

}

@9 Hashset。

 

package com.set;

public class HashsetText1 {

	public static void main(String[] args) {
		//创建学生对象
		Student stu =new Student("xangxang",34);
		System.out.println(stu);
		System.out.println(stu.hashCode());
		System.out.println("===============================");
		
		Student stu1 =new Student("tyuop",34);
		System.out.println(stu1);
		System.out.println(stu1.hashCode());
		System.out.println("================================");
		//查看哈希值二个对象
		
		Student stu2 =new Student("maomao",37);
		System.out.println(stu2);
		System.out.println(stu2.hashCode());
		//查看哈希值三个对象
		Student stu3 =new Student("nopains nogains",34);
		System.out.println(stu3);
		System.out.println(stu3.hashCode());
		//查看哈希值四个对象
		Student stu4 =new Student("nopains nogains",34);
		System.out.println(stu4);
		System.out.println(stu4.hashCode());
		System.out.println("================================");
		//查看哈希值五个对象
		Student stu5 =new Student("nopains nogains",34);
		System.out.println(stu5);
		System.out.println(stu5.hashCode());
		//查看哈希值六个对象
		Student stu6 =new Student("nopains nogains",34);
		System.out.println(stu6);
		System.out.println(stu6.hashCode());
		System.out.println(stu6.hashCode());
	
	}

}

package com.set;

public class HashsetText2 {

	public static void main(String[] args) {
		//创建学生对象
		Student stu =new Student("小小程序员",34);
		System.out.println(stu);
		System.out.println(stu.hashCode());
		System.out.println("===============================");
		
		Student stu1 =new Student("com on",34);
		System.out.println(stu1);
		System.out.println(stu1.hashCode());
		System.out.println("================================");
		//查看哈希值二个对象
		
		Student stu2 =new Student("毛毛非",37);
		System.out.println(stu2);
		System.out.println(stu2.hashCode());
		//查看哈希值三个对象
		Student stu3 =new Student("星星胡i11nogains",34);
		System.out.println(stu3);
		System.out.println(stu3.hashCode());
		//查看哈希值四个对象
		Student stu4 =new Student("nopains nogains",34);
		System.out.println(stu4);
		System.out.println(stu4.hashCode());
		System.out.println("================================");
		//查看哈希值五个对象
		Student stu5 =new Student("nopains nogains",34);
		System.out.println(stu5);
		System.out.println(stu5.hashCode());
		//查看哈希值六个对象
		Student stu6 =new Student("nopains nogains",34);
		System.out.println(stu6);
		System.out.println(stu6.hashCode());
		System.out.println(stu6.hashCode());
	
	}

}

package com.set;

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

public class Set2 {

	public static void main(String[] args) {
		Set s=new HashSet();
		s.add("今天天青");
		s.add("行万里路");
		s.add("加强学习java");
		s.add("自强不息");
		s.add("好好学习");
		for (int i = 0; i  
@10Map 
package Map;

import java.util.*;

public class HashMapDemo4 {

	private static final String HashMap = null;

	public static void main(String[] args) {
		HashMap hmap =new HashMap();
		hmap.put("name", "机熊");
		hmap.put("sex", "nan");
		hmap.put("id", "2345689");
		hmap.put("height", "145");
		hmap.put("age", "1003");
		//第一种方法keyset
		for(String key:hmap.keySet()) {
			System.out.println(key+"-----"+hmap.get(key));
			
		}
		System.out.println("=====================================");
		
		//第二种方法
		for(Map.Entry entry:hmap.entrySet()) {
			System.out.println(entry);
			
		}
		
		System.out.println("========");
		for(String key :hmap.keySet()) {
			System.out.println("key===="+key);
		}
		System.out.println("///");
		
		for(String value :hmap.values()) {
			System.out.println("value===="+value);
		}
		
		System.out.println("333333333333333");
		
		//keyset
		Iterator iterator=hmap.keySet().iterator();
		while(iterator.hasNext()) {
			String key=iterator.next();
			System.out.println(key+"    :    "+hmap.get(key));
		}
		
		//entryset
		Iterator> iterator1=hmap.entrySet().iterator();
		while(iterator.hasNext()) {
			Map.Entryentry= iterator1.next();
			System.out.println(entry.getKey());
			
		}
	}
}
		
		
	
		


 
@11项目实战， 
package com.web1;


import java.util.ArrayList;
import java.util.Scanner;

public class Reading {
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		ArrayList  array=new ArrayList();
		while(true){
			 System.out.println("--------欢迎来到学生图书管理系统  按以下执行	");
	            System.out.println("1 添 加 学 生喜爱的图书 "); 
	            System.out.println("2删 除 学 生不喜欢的数 "); 
	            System.out.println("3 修 改 学 生 图书编号"); 
	            System.out.println("4 查看所有学生信息"); 
	            System.out.println("5 退 出 "); 
	            System.out.println("请输入你的要选择的编号：");
	            Scanner sc=new Scanner(System.in);
	            String line=sc.nextLine();
	            switch(line){
	            case "1":
	            addStudent(array);break;
	            case "2":
	            deleteStudent(array);break;
	            case"3":
	            updateStudent(array);break;
	            case"4":
	            findAllStudent(array);break;
	           
	             //JVM退出
	            }
		}
	}
	public static void  addStudent(ArrayList  array ){
		
		String sid;
		while(true){
			System.out.println("请输入学生学号：");
			 Scanner sc=new Scanner(System.in);
			 
			sid =sc.nextLine();
			boolean flag=isUsed(array,sid);
			if(flag){
				 System.out.println("你输入的学号已经被占用，请重新输入");
			}else{
				 break;
			}
		} Scanner sc=new Scanner(System.in);
		 System.out.println("请输入学生姓名："); 
	        String name = sc.nextLine();

	        System.out.println("请输入学生年龄："); 
	        String age = sc.nextLine();

	        System.out.println("请输入学生居住地："); 
	        
	        String address = sc.nextLine();
	        Student s =new Student();
	        s.setAge(age);
	        s.setSid(sid);
	        s.setName(name);
	        s.setAddress(address);
	        array.add(s);
	        System.out.println("添加学生成功");
	}
	
	 public static boolean isUsed(ArrayList array, String sid) {
	        //如果与集合中的某一个学生学号相同，返回true;如果都不相同，返回false 
	        boolean flag = false;
	        for(int i=0; i array) {
	        //判断集合中是否有数据，如果没有显示提示信息
	        if (array.size() == 0) {
	        	System.out.println("无信息，请先添加信息再查询");
	        	//为了让程序不再往下执行，我们在这里写上return;
	        	return;
	    	}

	        //显示表头信息
	        //t其实是一个tab键的位置
	        System.out.println("学号ttt姓名tt年龄tt居住地");

	        //将集合中数据取出按照对应格式显示学生信息，年龄显示补充“岁” 
	        for (int i = 0; i < array.size(); i++) {
	        	Student s = array.get(i);
	       		System.out.println(s.getSid() + "t" + s.getName() + "t" + s.getAge() + "岁tt" + s.getAddress());
	        }
	    }

	    //定义一个方法，用于删除学生信息
	    public static void deleteStudent(ArrayList array) {
	    	//键盘录入要删除的学生学号,显示提示信息
	        Scanner sc = new Scanner(System.in);

	    	System.out.println("请输入你要删除的学生的学号："); 
	        String sid = sc.nextLine();

	        //在删除/修改学生 *** 作前，对学号是否存在进行判断
	        //如果不存在，显示提示信息
	        //如果存在，执行删除/修改 *** 作

	        int index = -1;


	        for (int i = 0; i < array.size(); i++) { 
	            Student s = array.get(i);
	            if (s.getSid().equals(sid)) { 
	                index = i;
	            break;
	            }
	                                               }
	            if (index == -1) {
	            	System.out.println("该信息不存在，请重新输入");
	            } else {
	            	array.remove(index);
	            	//给出删除成功提示System.out.println("删除学生成功");
	            }
	    }

	    //定义一个方法，用于修改学生信息
	    public static void updateStudent(ArrayList array) {
	        //键盘录入要修改的学生学号，显示提示信息
	        Scanner sc = new Scanner(System.in);

	        System.out.println("请输入你要修改的学生的学号："); 
	        String sid = sc.nextLine();

	        //键盘录入要修改的学生信息
	        System.out.println("请输入学生新姓名："); 
	        String name = sc.nextLine(); 
	        System.out.println("请输入学生新年龄："); 
	        String age = sc.nextLine(); 
	        System.out.println("请输入学生新居住地："); 
	        String address = sc.nextLine();

	        //创建学生对象
	        Student s = new Student(); 
	        s.setSid(sid); s.setName(name); 
	        s.setAge(age); 
	        s.setAddress(address);

	        //遍历集合修改对应的学生信息
	        for (int i = 0; i < array.size(); i++) { 
	            Student student = array.get(i);
	        	if (student.getSid().equals(sid)) { 
	                array.set(i, s);
	        	}
	        }

	        //给出修改成功提示System.out.println("修改学生成功");
	    }
}


 
package com.web1;


public class Student {
	public String sid;
	public String name;
	public  String age;
	public  String address ;
	
	public void Student(){}

	public Student(String sid, String name, String age, String address) {
		super();
		this.sid = sid;
		this.name = name;
		this.age = age;
		this.address = address;
	}

	public Student() {
		super();
		// TODO Auto-generated constructor stub
	}

	public String getSid() {
		return sid;
	}

	public void setSid(String sid) {
		this.sid = sid;
	}

	public String getName() {
		return name;
	}

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

	public String getAge() {
		return age;
	}

	public void setAge(String age) {
		this.age = age;
	}

	public String getAddress() {
		return address;
	}

	public void setAddress(String address) {
		this.address = address;
	}
	
	
}
 

 
 
					
										


					

						
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