The basic data type Notes
- Integer type: long> int> short> byte
- java default type is int type
- long a = 123
shows a value of type int assign a larger type long, than when the data type long long variable must be declared, and L must be added, modified data is declared as type long - long a = 2147483648L
- long a = 123
- java default type is int type
- Floating-point types: double> float
- java default type is double type
- Declare a float in java
- The integer to a float without F.
Float. 1 = B; - Assign a decimal number float need to add F.
Float B = 1.0;
- The integer to a float without F.
- boolean: true 、false
A type automatically upgrade, int type byte, short, char type of operation
- int = byte+byte
- int = short+short
- int = char - int
int char with the object when the first operation into byte code, such as: a ----> 97
public class Test1 {
public static void main(String[] args) { // 定义两个 byte类型变量 byte b1 = 10; byte b2 = 20; // 定义int 类型变量 b3 int b3 = b1 + b2; System.out.println("byte类型b1和b2的和为:"); System.out.println(b3); // 定义两个 short类型变量 short s1 = 1000; short s2 = 2000; // 定义int 类型变量 b3 int s3 = s1 + s2; System.out.println("short类型s1和s2的和为:"); System.out.println(s3); // 定义char类型变量 char ch1 = 'a'; // 定义int类型变量 int i1 = 30; // 定义int 类型变量 ch3 int ch3 = ch1 - i1; System.out.println("char类型ch1和int类型i1的差为:"); System.out.println(ch3); } }
Second, the automatic lift type, floating point type float, double operation
- float = long + int
- long = long +int
- double = double + int
double = float +double
class Test2 {public
public static void main (String [] args) {
// define variables of type int and long type variable i1 l1
int i1 = 100;
long l1 = 200 is;
// define variables add, and save i1 l1 and, and outputs.
long the Add = I1 + L1;
System.out.println ( "the Add values:" + the Add);
// l2 and define variables of type long float type variables F2
long l2 = 1000000;
float F2 = 0.45F;// 定义变量add2,保存l1和f1的和,并输出. float add2 = l2 + f2; System.out.println("add2的值:"+add2); // 定义 int类型变量i3 和 double类型变量d3 int i3 = 1000000; double d3 = 0.45; // 定义变量add3,保存i2和d1的和,并输出. double add3 = i3 + d3; System.out.println("add3的值:"+add3); //定义 float类型变量f2 和 double类型变量d2 float f4 = 1000000.789F; double d4 = 0.45; //定义变量add4,保存f2和d2的和,并输出. double add4 = f4 + d4; System.out.println("add4的值:"+add4); }}
Third, casts, a small -----> Large
- The type int into char type
char = (char) int The double type into int type
int = (int) doublethe Test3 {class public
public static void main (String [] args) {
// char type variable is defined ch, assigned to 'J'
char ch = 'J';
// ch lowercase variable 'j', and outputs
ch = (char) (CH + 32);
System.out.println (CH);// 定义char类型变量ch2,赋值为'a' char ch2 = 'a'; // 将变量ch2转换为大写'A',并输出 ch2 -= 32; System.out.println(ch2); // 定义double类型变量d3,int类型变量i3 double d3 = 3.5; int i3 = 100; // 定义变量sum3,保存d3和i3的和,将sum3去除小数部分并输出. double sum3 = d3 + i3; System.out.println("sum3的的值:" + sum3); System.out.println("sum3的整数部分的值:" + (int) sum3); // 定义double类型变量d4,int类型变量i4 double d4 = 5.8; int i4 = 300; // 定义int变量mul4,保存d4和i4乘积的整数部分,并输出 int mul4 = (int) (d4 * i4); System.out.println("mul4的整数部分值:"+mul4); }}
Fourth,%: Remainder Symbol
public static void main(String[] args) {
// 定义两个int类型变量a1和a2,分别赋值10,11,判断变量是否为偶数,拼接输出结果
int a1 = 10;
int a2 = 11;
boolean b1 = a1 % 2 == 0;
boolean b2 = a2 % 2 == 0;
System.out.println("10是偶数？" + b1);
System.out.println("11是偶数？" + b2);
// 定义两个int类型变量a3和a4,分别赋值12,13,判断变量是否为奇数,拼接输出结果
int a3 = 12;
int a4 = 13;
boolean b3 = a3 % 2 == 1;
boolean b4 = a4 % 2 == 1;
System.out.println("12是奇数？" + b3);
System.out.println("13是奇数？" + b4);
}Fifth, the difference of a ++ and ++ a
- ++ a, first add operation do
A = 20 is
++. 3% A
two-step operation:- a = a+1 = 21
- a % 3 = 21 % 3 =0
- a ++, Houjia Jia first computing
A = 20 is
A ++. 7%- a % 7 = 20 % 7 ≠ 0
- a = a + 1 =21
// define a variable of type int a, assigned 20. A
int = 20 is A;
// define a boolean variable BO, it determines whether ++ a divisible by 3, and whether a ++ divisible by 7, the results assigned to bo
Boolean a bo = ++ == 0 &&%. 3 a 7% ++ == 0;
// output value of a, the value of bo.
System.out.println ( "bo values:" BO +);
System.out.println ( "a value:" + a);
System.out.println ( "-------------");
// define a variable of type int B, assigned the value 20. a
int = 20 is B;
// define a boolean variable BO2, determines whether or b ++ divisible by 3, and whether ++ b divisible by 7, the results assigned to BO2
boolean BO2 = b ++ == 0 && 3% ++ b% 7 == 0;
value // of the output b, bo2's.
System.out.println ( "BO2 values:" + BO2);
System.out.println ( "b values:" + b );
}
VI ternary operator a> b true:? False
Ternary operator
表达式 ？表达式成立返回值：表达式不成立返回值 例： a > b ? true : false 如果a > b成立,则返回true, 否则，返回false{class Test6 public
public static void main (String [] args) {
// printNum method call in the main method
printNum ();
}private static void printNum() { // printNum方法中,定义int变量a赋值为9,b也赋值为9 int a = 9; int b = 9; // printNum方法中,定义int变量num赋值为++a. int num = ++a; // printNum方法中,定义boolean变量bo,使用三元运算符赋值,当num>=10,赋值为true,否则为false,打印bo的值 boolean bo = (num >= 10) ? true : false; System.out.println("bo的值"+bo); // printNum方法中,定义int变量num2赋值为b++. int num2 = b++; // printNum方法中,定义boolean变量bo2,使用三元运算符赋值,当num2>=10,赋值为true,否则为false,打印bo2的值 boolean bo2 = (num2 >= 10) ? true : false; System.out.println("bo2的值"+bo2); } }