package com.itheima.test7;
public class Test {
public static void main(String[] args) {
//定义一个长度为三的数组
Student[] arr= new Student[3];
//添加数据
Student s1 = new Student(1,"lisa",25);
Student s2 = new Student(2,"jisoo",26);
//Student s3 = new Student(3,"rose",25);
//赋值
arr[0] = s1;
arr[1] = s2;
//arr[2] = s3;
//1.添加一个对象
Student s4 = new Student(4,"jennie",25);
//唯一性判断,已存在，则不用添加
boolean flag = contains(arr,s4.getId());
if(flag){
System.out.println("id重复");
}else{
//数组已满，创建新数组，新数组长度=老数组+1；
//数组没满，直接添加 写成方法
int count = getCount(arr);
if(count== arr.length){
//已经存满,将老数组传递给新数组
Student[] newArr = createNewArr(arr);
//count是填充新元素的索引
newArr[count] = s4;
//2.遍历所有学生信息
printArr(newArr);
}else{
arr[count] = s4;
printArr(arr);
}
}
}
//打印元素，需要新数组老数组都打印所以要写方法,只需要打印，返回值为空
public static void printArr(Student[] arr){
for (int i = 0; i < arr.length ; i++) {
//数组要用变量接收
Student stu = arr[i];
if(stu!=null){
System.out.println(stu.getId()+","+ stu.getAge()+","+stu.getName());
}
}
}
//创建新数组,返回的是Student[]类型的数组
public static Student[] createNewArr(Student[] arr){
Student[] newArr =new Student[arr.length+1];
//循环遍历得到老数组中每一个元素
for (int i = 0; i < arr.length; i++) {
newArr[i] = arr[i];
}
return newArr;
}
//定义一个方法判断数组中存了几个元素
public static int getCount(Student[] arr){
//统计不为空的元素
int count= 0 ;
for (int i = 0; i < arr.length; i++) {
if(arr[i]!=null){
count++;
}
}
return count;
}
//需要数组、id,需要判断是否存在，所以要返回,用boolean
public static boolean contains(Student[] arr,int id){
for (int i = 0; i < arr.length; i++) {
//获取数组里的每一个学生对象
Student stu = arr[i];
if(stu != null){
//null不能直接使用
//获取数组中学生对象的id
int sid = stu.getId();
//比较
if (sid == id){
return true;
}
}
}
//循环结束后未找到直接判断错误
return false;
}
}
1 package com.itheima.test7;
2
3 public class Test3 {
4 public static void main(String[] args) {
5 //定义一个长度为三的数组
6 Student[] arr= new Student[3];
7 //添加数据
8 Student s1 = new Student(1,"lisa",25);
9 Student s2 = new Student(2,"jisoo",26);
10 Student s3 = new Student(3,"rose",25);
11 //赋值
12 arr[0] = s1;
13 arr[1] = s2;
14 arr[2] = s3;
15 //3.通过id删除信息
16 //如果存在，则删除，如果不存在，则提示删除失败
17 int index = getIndex(arr, 4);
18 if(index>=0){
19 //如果存在则删除（索引置空）
20 arr[index] = null;
21 //遍历数组
22 printArr(arr);
23 }else{
24 System.out.println("id不存在，删除失败");
25 }
26 }
27
28 //判断是否存在，所以必须返回
29 public static int getIndex(Student[] arr,int id){
30 for (int i = 0; i < arr.length; i++) {
31 //依次获得每一个学生对象
32 Student stu = arr[i];
33 //对stu进行一个非空判断
34 if(stu!=null){
35 int sid = stu.getId();
36 if(sid == id){
37 return i;
38 }
39 }
40
41 }
42 //循环结束后还没找到
43 return -1;
44 }
45 //打印元素，需要新数组老数组都打印所以要写方法,只需要打印，返回值为空
46 public static void printArr(Student[] arr){
47 for (int i = 0; i < arr.length ; i++) {
48 //数组要用变量接收
49 Student stu = arr[i];
50 if(stu!=null){
51 System.out.println(stu.getId()+","+ stu.getAge()+","+stu.getName());
52 }
53 }
54 }
55 }
1 package com.itheima.test7;
2
3 public class Test4 {
4 public static void main(String[] args) {
5
6 Student[] arr= new Student[3];
7
8 Student s1 = new Student(1,"lisa",25);
9 Student s2 = new Student(2,"jisoo",26);
10 Student s3 = new Student(3,"rose",25);
11
12 arr[0] = s1;
13 arr[1] = s2;
14 arr[2] = s3;
15
16 //id为2的年龄+1
17 int index =getIndex(arr,2);
18
19 //判断索引
20 if(index>=0){
21 //存在年龄+1
22 Student s = arr[index];
23 //把原来的年龄拿出来
24 int newAge = s.getAge() + 1;
25 //把+1之后的年龄塞回去
26 s.setAge(newAge);
27 printArr(arr);
28 }else {
29 System.out.println("不存在");
30 }
31 }
32 //判断是否存在，所以必须返回
33 public static int getIndex(Student[] arr,int id) {
34 for (int i = 0; i < arr.length; i++) {
35 //依次获得每一个学生对象
36 Student stu = arr[i];
37 //对stu进行一个非空判断
38 if (stu != null) {
39 int sid = stu.getId();
40 if (sid == id) {
41 return i;
42 }
43 }
44 }
45 //循环结束后还没找到
46 return -1;
47 }
48
49 //打印元素，需要新数组老数组都打印所以要写方法,只需要打印，返回值为空
50 public static void printArr(Student[] arr){
51 for (int i = 0; i < arr.length ; i++) {
52 //数组要用变量接收
53 Student stu = arr[i];
54 if(stu!=null){
55 System.out.println(stu.getId()+","+ stu.getAge()+","+stu.getName());
56 }
57 }
58 }
59 }
1 package com.itheima.test7;
2
3 public class Student {
4 private int id; //对字符串操作 先用int
5 private String name;
6 private int age;
7
8 public Student() {
9 }
10
11 public Student(int id, String name, int age) {
12 this.id = id;
13 this.name = name;
14 this.age = age;
15 }
16
17 public int getId() {
18 return id;
19 }
20
21 public void setId(int id) {
22 this.id = id;
23 }
24
25 public String getName() {
26 return name;
27 }
28
29 public void setName(String name) {
30 this.name = name;
31 }
32
33 public int getAge() {
34 return age;
35 }
36
37 public void setAge(int age) {
38 this.age = age;
39 }
40 }
标签：arr,删除,stu,int,id,面向对象,添加,Student,public From： https://www.cnblogs.com/Wang0626/p/17232582.html