Create a marker for range with switch statement in java

Question

so I have an assignment that I need to use a switch statement to identify a marker for range of random values The question is like this:

Using switch statements, please identify the different ranges. Hence, follow the suggested markers:

"o" for numbers between (0,5];

"x" for numbers between (5, 10];

"s" for numbers between (10, 15];

"*" for numbers bigger than 15;

import java.util.*;

public class Problem01 {
    public static void main(String[] args) {
        //create random integer
        Random ran = new Random();
        int sum = 0;
        for (int i = 1; i <= 10; i++ ) {
            int random = ran.nextInt(20);
            //Printing the random number
            System.out.print("Number " + "(" + random + "): ");

            //Loop to print markers
            for(int j = 1; j <= random; j++) {
               //I don't know how to use the switch statement at this point, I tried everything and nothing work
            }
        }
    }
}

I have searched on the internet a lot but none of the way work, can you guys help me, thanks a lot

What about a `switch` statement do you not understand? – Polygnome Sep 18 '20 at 09:57 — Polygnome, Sep 18 '20 at 09:57

pavan-kalyan · Accepted Answer · 2020-09-18T10:26:17.923

You can do the following:

import java.util.*;

public class Problem01 {
    public static void main(String[] args) {
        //create random integer
        Random ran = new Random();
        int sum = 0;
        for (int i = 1; i <= 10; i++ ) {
            int random = ran.nextInt(20);
            //Printing the random number
            System.out.print("Number " + "(" + random + "): ");

            switch ((random-1)/5) {
                case 0:
                    System.out.println("o");
                    break;
                case 1:
                    System.out.println("x");
                    break;
                case 2:
                    System.out.println("s");
                    break;
                default: //to handle case where the number is bigger than 15
                    System.out.println("*");
                    break;

            }
        }
    }
}

I'm not sure why you needed the inner loop.

This is the generated output for the above program.

Number (1): o
Number (10): x
Number (5): o
Number (13): s
Number (9): x
Number (13): s
Number (6): x
Number (16): *
Number (16): *
Number (10): x

edit: There is no direct way to use custom ranges with switch statements. This has been answered here

Nowhere Man · Answer 2 · 2020-09-18T11:06:15.457

The most straightforward solution would be just to use multiple case options for each number:

String s = "$";
switch (j) {
    case 1: case 2: case 3: case 4: case 5:
        s = "x"; break;
    case 6: case 7: case 8: case 9: case 10:
        s = "o"; break;
    case 11: case 12: case 13: case 14: case 15:
        s = "s"; break;
    default:
        s = "*"; break;
}
System.out.println(x);

A better advanced version is to divide the input parameter by 5 (correct by 1) to reduce the number of cases:

switch ((j - 1) / 5) {
    case 0:
        s = "x"; break;
    case 1:
        s = "o"; break;
    case 2:
        s = "s"; break;
    default:
        s = "*"; break;
}

Also it's possible to get rid of switch completely by calculating an index in the array using % operator:

public static final String[] OPTS = {"X", "O", "S", "*"};
//...
String s = j < 20 ? OPTS[(j - 1) / 5 % OPTS.length] : OPTS[OPTS.length - 1];

Update

Another workaround could be to use a class/enum wrapper for the range (though it would be using if inside):

public enum RANGE {
    X(0, 5, "x"),
    O(5, 10, "o"),
    S(10, 15, "s"),
    OTHER(0, -1, "*");

    private final int min;
    private final int max;
    private final String sym;

    RANGE(int min, int max, String sym) {
        this.min = min;
        this.max = max;
        this.sym = sym;
    }
        
    public String getSym() {return sym; }

    static RANGE from(int n) {
        return Arrays.stream(RANGE.values())
                     .filter(r -> r.min < n && n <= r.max)
                     .findFirst().orElse(RANGE.OTHER);
    }
}

// actually, switch seems redundant:
switch(RANGE.from(j)) {
    case X: // do something
        break;
    // ...
    OTHER:
    default:
        // no range found
        break;
}

Create a marker for range with switch statement in java

2 Answers2