1.算术运算 + 加 - 减 * 乘 / 除 % 取模（取余数）
+= -= *= /= %= 例1 package ddouble;


public class ddouble {
public static void main(String[] args){
int a=1;
int b=2;
System.out.println(a+b);
System.out.println(a-b);
System.out.println(a*b);
System.out.println((double)a/b);
}
} 例2（%） package ddouble;


public class ddouble {
public static void main(String[] args){
int a=2;
int b=3;
System.out.println(b%a);
}
} 例3 package ddouble;


public class ddouble {
public static void main(String[] args){
int a=2;
int b=3;
int c=4;
int d=5;
int e=6;
a+=1;
b-=1;
c*=2;
d/=2;
e%=4;
System.out.println(a);
System.out.println(b);
System.out.println(c);
System.out.println(d);
System.out.println(e);
}
}