数据类型/基本类型

1.java的数据类型

 基本类型(8)

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 true 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

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)

(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');