java学习笔记（四）

package Test;
public class StuTest {
    public static void main(String[] args) {
        Students[] stuArr = new Students[3];
        Students s1 = new Students(1,"张三",18);
        Students s2 = new Students(2,"李四",19);
        Students s3 = new Students(3,"王五",20);
        stuArr[0]=s1;
        stuArr[1]=s2;
        stuArr[2]=s3;
        for (int i = 0; i < stuArr.length; i++) {
            Students s = stuArr[i];
            System.out.println(s.getId()+" "+s.getName()+" "+s.getAge());
        }
    }
}

package Test;
public class StuTest {
    public static void main(String[] args) {
        Students[] stuArr = new Students[3];
        Students s1 = new Students(1,"张三",18);
        Students s2 = new Students(2,"李四",19);
//        Students s3 = new Students(3,"王五",20);
        stuArr[0]=s1;
        stuArr[1]=s2;
//        stuArr[2]=s3;
        /*for (int i = 0; i < stuArr.length; i++) {
            Students s = stuArr[i];
            System.out.println(s.getId()+" "+s.getName()+" "+s.getAge());
        }*/
        Students s4=new Students(4,"zhaoliu",21);
        boolean flag = contains(stuArr,s4.getId());
        if (flag){
            //y
            System.out.println("the id is contain! ");
        }else {
            //no
            int count = getCount(stuArr);
            if(count == stuArr.length){
                //over
                Students[] newArr = creatNewArr(stuArr);
                newArr[count]=s4;
                printArr(newArr);
            }else {
                //no over
                stuArr[count]=s4;
                printArr(stuArr);
            }
        }
    }
    //遍历数组
    public static void printArr(Students[] arr){
        for (int i = 0; i < arr.length; i++) {
            Students stu = arr[i];
            if (stu!= null){
                System.out.println(stu.getId()+" "+stu.getName()+" "+stu.getAge());
            }
        }
    }
    //计算数组是否存满
    public static boolean contains(Students[] arr,int id){
        for (int i = 0; i < arr.length; i++) {
            Students stu = arr[i];
            if(stu != null){
                int sid = stu.getId();
                if(sid ==id )
                    return true;
            }
        }
    //循环结束后，return
        return false;
    }
    //计算数组已经存了几个函数
    public static int  getCount(Students[] arr){
        int count =0;
        for (int i = 0; i < arr.length; i++) {
            if(arr[i]!=null){
                count++;
            }
        }
        return count;
    }
    //
    public static Students[] creatNewArr(Students[] arr){
        Students[] newArr = new Students[arr.length+1];
        for (int i = 0; i < arr.length; i++) {
             newArr[i] = arr[i];
        }
        return newArr;
    }
}