Java BASICS (2) and java Basics

Java BASICS (2) and java Basics

1. absolute path/relative path

1> complete absolute path URL

2> the relative path/starting with "/" indicates the entire web project.

3> relative paths not starting with "/"./indicates the current path./indicates the upper path.

Two-thread status

New ready for execution blocking death

Algorithm Analysis

There are n floors of stairs and a maximum of m floors in each step. How many crawling methods are there?

Analysis: one layer of stairs, one method of crawling, two types of three layers, three types of four layers, namely f (n) = f (n-1) + f (n-2) + f (n-3) + .. + f (0)

At most m layers, f (n) = f (n-1) + f (n-2) + f (n-3) +... + f (n-m) is recursive.

The following are core algorithm programs:

Public int getMethodCount (int n, int m ){

If (0 = n ){

Return 1; // The number of steps is 0.

} Else if (1 = total ){

Return 1; // The number of steps is 1.

} Else {

Int result = 0;

For (int I = 0; I <= n; I ++ ){

If (I <= m ){

Result + = getMethodCount (n-I, m );

}

}

Return result;

}

}

4. list all the combinations of numbers in an array, for example, 1 and 2, and 1, 2, 12, and 21.

The complete code is as follows:

Public static void main (String [] args ){

String [] array = new String [] {"1", "2 "};
ListAll (Arrays. asList (array ),"");
}

Public static void listAll (List ca, String p) {90
System. out. println (p );
For (int I = 0; I <ca. size (); I ++ ){
List temp = new Alibaba List (ca );
ListAll (temp, p + temp. remove (I ));
}
}