枚举类
public class EnumTest {
public static void main(String[] args) {
Size s=Size.SMALL;
Size t=Size.LARGE;
System.out.println(s==t);
System.out.println(s.getClass().isPrimitive());
Size u=Size.valueOf("SMALL");
System.out.println(s==u); //true
for(Size value:Size.values()){
System.out.println(value);
}
}
}
enum Size{SMALL,MEDIUM,LARGE};
输出
false
false
true
SMALL
MEDIUM
LARGE
原码，反码，补码
public class a02Test2 {
public static void main(String[] args) {
int a = 100;
int b = -50;
System.out.println(a >> 1);
System.out.println(b >> 1);
}
}
输出
50
-25
package TestCode3;
public class TestDouble {
public static void main(String args[]) {
System.out.println("0.05 + 0.01 = " + (0.05 + 0.01));
System.out.println("1.0 - 0.42 = " + (1.0 - 0.42));
System.out.println("4.015 * 100 = " + (4.015 * 100));
System.out.println("123.3 / 100 = " + (123.3 / 100));
}
}
输出
0.05 + 0.01 = 0.060000000000000005
1.0 - 0.42 = 0.5800000000000001
4.015 * 100 = 401.49999999999994
123.3 / 100 = 1.2329999999999999
import java.math.BigDecimal;
public class TestBigDecimal
{
public static void main(String[] args)
{
BigDecimal f1 = new BigDecimal("0.05");
BigDecimal f2 = BigDecimal.valueOf(0.01);
BigDecimal f3 = new BigDecimal(0.05);
System.out.println("下面使用String作为BigDecimal构造器参数的计算结果：");
System.out.println("0.05 + 0.01 = " + f1.add(f2));
System.out.println("0.05 - 0.01 = " + f1.subtract(f2));
System.out.println("0.05 * 0.01 = " + f1.multiply(f2));
System.out.println("0.05 / 0.01 = " + f1.divide(f2));
System.out.println("下面使用double作为BigDecimal构造器参数的计算结果：");
System.out.println("0.05 + 0.01 = " + f3.add(f2));
System.out.println("0.05 - 0.01 = " + f3.subtract(f2));
System.out.println("0.05 * 0.01 = " + f3.multiply(f2));
System.out.println("0.05 / 0.01 = " + f3.divide(f2));
}
}
输出
下面使用String作为BigDecimal构造器参数的计算结果：
0.05 + 0.01 = 0.06
0.05 - 0.01 = 0.04
0.05 * 0.01 = 0.0005
0.05 / 0.01 = 5
下面使用double作为BigDecimal构造器参数的计算结果：
0.05 + 0.01 = 0.06000000000000000277555756156289135105907917022705078125
0.05 - 0.01 = 0.04000000000000000277555756156289135105907917022705078125
0.05 * 0.01 = 0.0005000000000000000277555756156289135105907917022705078125
0.05 / 0.01 = 5.000000000000000277555756156289135105907917022705078125
package TestCode3;
public class Test1 {
public static void main(String[] args) {
int X=100;
int Y=200;
System.out.println("X+Y="+X+Y);
System.out.println(X+Y+"=X+Y");
}
}
package TestCode3;
public class Test1 {
public static void main(String[] args) {
int X=100;
int Y=200;
System.out.println("X+Y="+X+Y);
System.out.println(X+Y+"=X+Y");
}
}
输出
X+Y=100200
300=X+Y
字符串拼接-从前往后
生成100以内随机算式
import java.util.Random;
public class randomMath {
public static void main(String[] args) {
Random ch = new Random();
Random r = new Random();
Character[] chArr = {'+','-','*','/'};
for (int i = 0; i < 30; i++) {
int first = r.nextInt(100);
int second = r.nextInt(99)+1;
char c = chArr[ch.nextInt(4)];
System.out.print(first);
System.out.print(c);
System.out.println(second + " = ");
}
}
}