Java中包装类

package com.atguigu;

public class Wrapper {

    @org.junit.Test
    public void toWrapper() {
        int num = 10;
        Integer integer = new Integer(num);
        System.out.println(integer);//10

        Integer integer1 = new Integer("123");
        System.out.println(integer1);//123

        Float f = new Float(12.3f);
        Float f1 = new Float(12.3);
        System.out.println(f);//12.3
        System.out.println(f1);//12.3

        Boolean b = new Boolean(true);
        Boolean b1 = new Boolean("true");
        Boolean b2 = new Boolean("123");
        System.out.println(b);//true
        System.out.println(b1);//true
        System.out.println(b2);//false
    }

}

@org.junit.Test
    public void toBasic(){
        Integer integer = new Integer(12);
        int a  = integer.intValue();
        System.out.println(a);//12

        Float f = new Float(12.5f);
        float f1 = f.floatValue();
        System.out.println(f1);//12.5
    }

@org.junit.Test
    public void encasement() {
        int a = 1;
        //自动装箱，基本数据类型可以直接赋给类
        Integer integer = a;
        System.out.println(integer);//1

        //自动拆箱，类可以直接赋给基本数据类型
        int b = integer;
        System.out.println(b);//1
    }

@org.junit.Test
    public void toStr(){
        int num = 1;

        //方式一：连接运算
        String str = num + "";
        System.out.println(str.getClass());//class java.lang.String

        //方式二
        String s = String.valueOf(num);
        System.out.println(s.getClass());//class java.lang.String
    }

@org.junit.Test
    public void toBasic2(){
        String s = "12.5";//如果数据不能转换，会报numberFormat异常

        //调用包装类的方法
        Float v = Float.parseFloat(s);
        System.out.println(v.getClass());//class java.lang.Float
    }