Java face question 1

1. ask for a 1calculation! +2! +......+60! The result?

If you want to calculate data, then you must first have a data type, this time can only use Double The data type.

Implement one: done directly through the code

Public class testdemo{
public static void Main (string[] args) {

Double sum = 0.0;// Save the final calculation result
         for (int x =1;x<=60;x++) {
             double temp = 1.0;//save results for each factorial
             for (int y = 1;y <= x;y++) {
                 temp *= y;//calculating factorial
             }
             sum += temp;
        
        }
&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;SYSTEM.OUT.PRINTLN ("calculation result" +sum);
    
    }


}

Implementation two: Use recursion to complete, if you want to use recursion to complete the need two times recursion

Recursive operation one: responsible for the factorial operation of each data;

Recursive operation two: Add the results of each recursive operation

Public classtestdemo{
public static void Main (string[] args) {

System.out.println ("Calculation result "+sum (60));

}

public static double sum (int num) {
if (num==1) {
return 1;
}else{

return Mul (num) +sum (num-1);
}

}
public static double mul (int num) {
if (num = = 1) {
return 1;
}else{

Return Num*mul (num-1);
}

}

}

2. write a method that can turn an integer into a binary output.

Implement one: using common code to implement

public class testdemo{
public static void Main (string[] args) {
int num = 10;//10010

String str = "";// define string Save
while (num!=0) {// already has no value

str= (num%2) +str;

NUM=NUM/2;

}
System.out.println (str);
}

implementation two: by Recursive implementation

public class testdemo{
public static void Main (string[] args) {
Tobinary (18);

}
public static voidtobinary (int num) {

If (num==0) {

Return;

}

Tobinary (NUM/2);

System.out.println (num%2);

}
}

3.

5 people sat together and asked how old the 5th person was, and he said he was 2 years older than the 4th person. Asked how old the 4th person was, he said he was 2 years older than the 3rd man. Asked how old the 3rd person was, he said he was 2 years older than the 2nd man. Asked how old the 2nd person was, he said he was 2 years older than the 1th man. Asked how old the 1th person was, he said it was 8 years old. How old is the 5th one?

Implementation one: using plain code implementation

public class testdemo{
public static void Main (string[] args) {
int age = 8;

for (int x=0;x<4;x++) {

Age + = 2;

}

System.out.println (age);

}
}

Implementing two: Using recursive implementations

public class testdemo{
public static void Main (string[] args) {
Age (5);

}

public static int age (int num) {

if (num==1) {

RETURN8;

}

Return 2+age (num-1);

}
}

This article is from the "10281302" blog, please be sure to keep this source http://10291302.blog.51cto.com/10281302/1688314

Java face question 1