Implementation of Android sorting-for beginners

Bad code:

View plain
Int [] iArray = {12,122,123,124, 1 ,};
 
// Sort iArray
Int iMin = 999999;
Int indexMin = 0;
Int iTmp = 0;
For (int I = 0; I <iArray. length; I ++ ){
// Find the smallest
For (int j = I; j <iArray. length; j ++ ){
If (iMin> iArray [j]) {
IMin = iArray [j];
IndexMin = j;
}
}
// Put it at the beginning
ITmp = iArray [I];
IArray [I] = iArray [indexMin];
IArray [indexMin] = iTmp;
}
 
For (int I = 0; I <iArray. length; I ++ ){
System. out. print (iArray [I] + ",");
}
System. out. println ();

First, there is a BUG. The minimum value is initialized with 999999. If the number in the array is greater than 999999, the sorting will not proceed.

You can change 999999 to Integer. MAX_VALUE.

Second, you just sort an array and do not need to write it yourself. Arrays contains the sorting function. The program can be changed:

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Int [] iArray = {12,122,123,124, 1 ,};
 
// Sort iArray
Arrays. sort (iArray );
 
For (int I = 0; I <iArray. length; I ++ ){
System. out. print (iArray [I] + ",");
}
System. out. println ();

So what if we want to sort an object instead of an integer?

For example, we have a class:

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Public class Point {
Private int x;
Private int y;
Public Point (int x, int y ){
This. x = x;
This. y = y;
}
}

Now we need to sort an array of this class. Can I use the sorting function of the system. Of course.

First, our class must implement the interface: Comparable. That is, this object must be comparable.

Second, we need to implement the function defined by this interface: compareTo.

The modified class is as follows:

View plain
Public class Point implements Comparable {
Private int x;
Private int y;
Public Point (int x, int y ){
This. x = x;
This. y = y;
}

Private int getMix (){
Return (x <8) + y;
}

@ Override
Public int compareTo (Object o ){
Point other = (Point) o;
Return getMix ()-other. getMix ();
}

@ Override
Public String toString (){
Return "(" + x + "," + y + ")";
}
}

The sorting code is as follows:

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// Randomly generate 5 objects
Random random = new Random ();
List <Point> lst = new ArrayList <Point> ();
For (int I = 0; I <5; I ++ ){
Lst. add (new Point (random. nextInt (100), random. nextInt (100 )));
}
Point [] pArray = lst. toArray (new Point [lst. size ()]);
 
// Sort the Point Array
Arrays. sort (pArray );
 
For (int I = 0; I <pArray. length; I ++ ){
System. out. print (pArray [I] + ",");
}
System. out. println ();

In the compareTo function, the values of the objects to be compared are generally the values corresponding to the objects to be compared. If compareTo returns a negative number, it indicates that the current object is smaller than the input parameter.

Author: "yihui823 column"