在千锋“逆战”学习第 3 天;
奋斗没有终点,任何时候都是一个起点;
今天学习的课程有4类8种基本数据类型,String引用数据类型,数据类型的自动以及强制转换;
中国加油!武汉加油!千锋加油!
我自己加油!
public class TestDateType{
public static void main(String[] args){
byte b = -128;
short s = 32767;
int i = 210000000;
long l1=100;
long l2 = 3000000000000L;
System.out.println(b);
System.out.println(s);
System.out.println(i);
System.out.println(l1);
System.out.println(l2);
System.out.println(Long.MAX_VALUE);
//此为java内一种类的功能:long整型的最大取值
System.out.println("++++++++++++");
float f = 1.23F;
double d1 = 200;
//此隐含了int转double型的自动转换
double d2 = 2E2;
double d3 = 200.0;
//d1,d2,d3为3个不同的表达方式。
System.out.println(f);
System.out.println(d1);
System.out.println(d2);
System.out.println(d3);
System.out.println("+++++++++++++");
boolean b1 = true;
boolean b2 = 3+2<4;
System.out.println(b1);
System.out.println(b1);
System.out.println("+++++++++++++");
char c1 = '中';
char c2 = 22269;
char c3 = '\u0041';
System.out.println(c1);
System.out.println(c2);
System.out.println(c3);
System.out.println("+++++++++++++");
String str = "武汉 加油";
System.out.println(str);
char c4 = '\'';
System.out.println("\'\\\"\tfright");
System.out.println(c4);
System.out.println("+++++++++++++");
byte bb1 = 2;
int ii1 = bb1;
System.out.println(ii1);
int ii2 = 128;
byte bb2 = (byte)ii2;
System.out.println(bb2);
/*
整型:2进制
byte--->short:自动转换
byte:8位
0000 0001
short:16位
0000 0000 1000 0000
short-->byte:强制转换,因为数据存在不安全性
0000 0000 1000 0000
1000 0000
且整数都是以补码存储
*/
double dd1 = 1.23;
float ff1 = (float)dd1;
System.out.println(ff1);
float ff2 = 4.56F;
long ll1 = (long)ff2;
System.out.println(ll1);
char cc1 = 65;
int ii3 = cc1;
System.out.println(113);
short ss1 = -65;
char cc2 = (char)ss1;
System.out.println(cc2);
//(-65-->?)语法虽然正确,但是计算机却找不到-65的编码对应
}
}