1.java的数据类型
基本类型(8种)
引用类型
2.8种基本类型
|
Byte |
1 |
-128~127 -2^7~2^7-1 |
|
Short |
2 |
-2^15~2^15-1 |
|
Int |
4 |
-2^31~2^31-1 |
|
Long |
8 |
-2^63~2^63-1 |
|
Float |
4 |
单精度IEEE-754规范(美国电子电气工程师协会) |
|
Double |
8 |
双精度 |
|
Char |
2 |
字符,或字符的整数编码 0~65535 0~2^16-1 |
|
Boolean |
1 |
布尔值 真 true 假 false |
基本类型
package day0201;
public class Test1 {
public static void main(String[] args) {
//定义8个变量,保存4种整数的最大值和最小值
byte a = -128;
byte b = 127;
//jdk类库种的java.short.Short
//保存着short类型的最小值
short c = Short.MIN_VALUE;
short d = Short.MAX_VALUE;
int e = Integer.MIN_VALUE;
int f = Integer.MAX_VALUE;
long g = Long.MIN_VALUE;
long h = Long.MAX_VALUE;
System.out.println(a);
System.out.println(b);
System.out.println(c);
System.out.println(d);
System.out.println(e);
System.out.println(f);
System.out.println(g);
System.out.println(h);
}
}
变量交换
import java.util.Scanner;
public class Test1 {
public static void main(String[] args) {
System.out.print("输入整数a:");
int a = new Scanner(System.in).nextInt();
System.out.print("输入整数b:");
int b = new Scanner(System.in).nextInt();
int c = a;
a = b;
b = c;
System.out.println("a ="+a);
System.out.println("b ="+b);
}
}
浮点数
package day0201;
public class Test2 {
public static void main(String[] args) {
//a b c d 4个变量保存浮点数的最小/大值
float a = Float.MIN_VALUE;
float b = Float.MAX_VALUE;
double c = Double.MIN_VALUE;
double d = Double.MAX_VALUE;
System.out.println(a);
System.out.println(b);
System.out.println(c);
System.out.println(d);
}
}
自由落体距离
package day0203;
import java.util.Scanner;
public class Test1 {
public static void main(String[] args) {
System.out.print("输入下落时间(秒):");
double t = new Scanner(System.in).nextDouble();
double d = 0.5 * 9.8 * t * t;
System.out.println(t + "秒,下落了" + d + "米");
}
}
Char
unicode编码的字符
|
0 |
|
|
1 |
|
|
2 |
|
|
… |
|
|
65 |
A |
|
66 |
B |
|
… |
|
|
97 |
a |
|
98 |
b |
|
20013 |
中 |
|
65535 |
|
范围0~65535
Char c1 = ‘a’;
Char c1 = 97;
CHAR
package day0201;
public class Test3 {
public static void main(String[] args) {
char c1 = 'a';
char c2 = 97;
char c3 = 'b';
char c4 = 98;
char c5 = '中';
char c6 = 20013;
System.out.println(c1);
System.out.println(c2);
System.out.println(c3);
System.out.println(c4);
System.out.println(c5);
System.out.println(c6);
System.out.println('刘'+0);
System.out.println('立'+0);
System.out.println('博'+0);
}
}
3.基本类型的字面值规则(5条)
(1)整数字面值:int
int a =6364; Long a = 99999999999;//右侧是int类型超出int范围
(2)byte/short/char 三种比int小的整数类型
可以用范围内的值,直接赋值
Byte a =127;//右侧是byte类型 Byte a = 128;//超出范围,右侧是int类型
(3)浮点数字面值是double
Double a = 3.14; Float a = 3.14;//右侧是double类型
(4)字面值后缀
L long Long A = 999999999L; F float Float a = 3.14F; D double Double a = 3.14D;
(5)进制前缀
0x 十六进制
0 八进制
\u char类型 16进制
System.out.println('\u0061');
System.out.println('\u0062');
System.out.println('\u5218');
System.out.println('\u7acb');
System.out.println('\u535a');