整数short ,int ,long
浮点数 float double
大整数类biginteger(大整数),bigdecimal(大浮点数),因为整数类和浮点数类所表示的数字都有界限范围,但是大数类没有,可以无穷大
随机数类 random
工具类math
![](https://img.laitimes.com/img/_0nNw4CM6IyYiwiM6ICdiwiI0gTMx81dsQWZ4lmZf1GLlpXazVmcvwFciV2dsQXYtJ3bm9CX9s2RkBnVHFmb1clWvB3MaVnRtp1XlBXe0xCMy81dvRWYoNHLwEzX5xCMx8FesU2cfdGLwMzX0xiRGZkRGZ0Xy9GbvNGLpZTY1EmMZVDUSFTU4VFRR9Fd4VGdsYTMfVmepNHLrJXYtJXZ0F2dvwVZnFWbp1zczV2YvJHctM3cv1Ce-cmbw5yM3ADO2YGZ3UTNhVjMxEWZyYzXwUDNxQTMzAzLchDMyIDMy8CXn9Gbi9CXzV2Zh1WavwVbvNmLvR3YxUjLyM3Lc9CX6MHc0RHaiojIsJye.png)
包装类和基本类型的范围是一样的
package mooc_8_01;
public class IntegerTest {
public static void main(String[] args) {
short a1 = 32767;
System.out.println(a1);
//short a2 = 32768;error 越界(最多到32767)
int b1 = 2147483647;
System.out.println(b1);
//int b2 = 2147483648; error 越界
long c1 = 1000000000L;//后面要加L
System.out.println(c1);
long c2 = 2147483647;//隐式做了从int变成long的操作
System.out.println(c2);
long c3 = 2147483648L;//去掉L将报错;
System.out.println(c3);
}
}
package mooc_8_01;
public class mooc_8_02 {
public static void main(String[] args) {
float f1 = 1.23f;
//float f2 = 1.23;//error ,float赋值必须带f
double d1 = 4.56d;
double d2 = 4.56;//double 可以省略末尾的d
System.out.println(f1);
System.out.println((double)f1);//强制类型转换
System.out.println(d1);
System.out.println((float)d2);
System.out.println(f1==1.22999999f);//1.23是等于1.2999999的,表示的不准确
System.out.println(f1-1.22999999f);
System.out.println(d2==4.5599999999d);
System.out.println(d2-4.5599999999d);
}
}