java学习part22包装类

119-面向对象(高级)-包装类的理解_基本数据类型与包装类间的转换_哔哩哔哩_bilibili

1.包装类

 

2.基本转包装方式

2.1new方式

 

源码

2.2valueof（）

3.包装转基本

 4.基本类型和包装类型的默认值不一样

比如boolean默认false

Boolean默认null（对象）

通过初始值的不一样，可以分辨某些对象是否初始化过还是归零了

5.自动装箱拆箱

 6.String和其他类型转换

import java.util.Scanner;
import java.util.Vector;

public class Main {
    //求最大
    public static void main(String[] args) {
        Main m = new Main();
        System.out.println(  m.maxScoreFunc() );

    }

    int maxScoreFunc2(){
        Vector v = new Vector();
        Scanner scan = new Scanner(System.in);
        int maxScore = 0;
        while(true){
            System.out.println("print in");
            int intScore = scan.nextInt();
            if(intScore < 0){
                break;
            }
          //  Integer score = Integer.valueOf(intScore);
            //自动装箱成对象放入向量
            v.addElement(intScore);
            maxScore = intScore > maxScore? intScore:maxScore;
        }
        for(int i=0;i < v.size();i++){
            //取对象拆箱
            Object objScore = v.elementAt(i);
            int intScore = (Integer) objScore;
            if(maxScore - 10 > intScore){
                System.out.println("B等级");
            }
        }

        return maxScore;
    }


    int maxScoreFunc(){
        Scanner scan = new Scanner(System.in);
        int maxScore = 0;
        while(true){
            System.out.println("print in");
            int intScore = scan.nextInt();
            if(intScore < 0){
                break;
            }
            maxScore = intScore > maxScore? intScore:maxScore;
        }
        //System.out.println(maxScore);
        return maxScore;
    }


}