Java基础之包装类

package cn.zhz.Instance;

public class Test02 {
    public static void main(String[] args) {
        //属性
        System.out.println(Integer.MAX_VALUE);
        System.out.println(Integer.MIN_VALUE);
        //物极必反:超出了Int类型的范围
        System.out.println(Integer.MAX_VALUE + 1);
        System.out.println(Integer.MIN_VALUE - 1);
    }
}

package cn.zhz.Instance;

public class Test03 {
    public static void main(String[] args) {
        Integer i1 = new Integer(13);
        System.out.println(i1.toString());
        Integer i2 = new Integer("12");
        System.out.println(i2);
    }
}

package cn.zhz.Instance;

public class Test04 {
    public static void main(String[] args) {
        //自动装箱:int-->Integer
        Integer i = 12;
        System.out.println(i);
        //自动拆箱:Integer-->int
        Integer i2 = new Integer(123);
        int num = i2;
        System.out.println(num);
    }
}

package cn.zhz.Instance;

public class Test05 {
    public static void main(String[] args) {
        //compareTo():只返回三个值，要么是0 -1 1
        Integer i1 = new Integer(6);
        Integer i2 = new Integer(12);
        System.out.println(i1.compareTo(i2));//return (x < y) ? -1 ((x == y) ? 0 : 1)
        //equals():Integer是对object中的equals方法进行了重写，比较的是底层封装的那个value的值
        //Integer对象是通过new关键字来创建对象
        Integer i3 = new Integer(12);
        Integer i4 = new Integer(12);
        System.out.println(i3 == i4);//false 因为==比较的是两个对象的地址
        boolean flag = i3.equals(i4);
        System.out.println(flag);
        //Integer对象是通过自动装箱来完成的
        Integer i5 = 12;
        Integer i6 = 12;
        System.out.println(i5.equals(i6));//true
        System.out.println(i5 == i6);
        /*
         * 如果自动装箱在-128~127之间，那么比较的就是具体的数值，否则，比较的就是对象的地址
         * */
        //intvalue():
        Integer i7 = 130;
        int i = i7.intValue();
        System.out.println(i);
        //parseInt(String s):String -->int
        int i8 = Integer.parseInt("12");
        System.out.println(i8);
        //toString():
        Integer i10 = 130;
        System.out.println(i10.toString());
    }
}