Objective:

This assignment helps students understand how to implement interfaces in Java—a crucial concept in software engineering.

Task:

Implement the given Utilities211Interface interface in a class called Utilities211Code.java.
Test your implementation using the provided Utilities211Driver.java class.
Ensure your code follows good Java coding standards, is well-commented, and produces the correct results.

Utilities211Interface.java (Interface Specification)

java

// Utilities211Interface.java
public interface Utilities211Interface {
    /**
     * Method reads a string and verifies that the string contains at least 2 non-blank characters.
     * For example:
     *   " a b "   -> true
     *   " x "     -> false
     *   ""        -> false
     *   "   "     -> false
     *   "123abc"  -> true
     * Length of the string does not determine validity.
     * @param s the string to be tested
     * @return true if at least 2 non-blank characters, false otherwise
     */
    boolean validString(String s);

    /**
     * @param d number to be tested
     * @return 1 if the number is positive, -1 if negative, 0 if zero
     */
    int numberSign(double d);

    /**
     * Receives 2 int numbers and counts the numbers in the range between them (exclusive).
     * Example: range(20, 33) returns 13, range(12, -5) returns 17
     * @param i1 first integer
     * @param i2 second integer
     * @return the count of integers in the range (exclusive)
     */
    int range(int i1, int i2);
}

Utilities211Code.java (Implementation)

java

// Utilities211Code.java
public class Utilities211Code implements Utilities211Interface {
    @Override
    public boolean validString(String s) {
        if (s == null) return false;
        int count = 0;
        for (char c : s.toCharArray()) {
            if (!Character.isWhitespace(c)) count++;
            if (count >= 2) return true;
        }
        return false;
    }

    @Override
    public int numberSign(double d) {
        if (d > 0) return 1;
        if (d < 0) return -1;
        return 0;
    }

    @Override
    public int range(int i1, int i2) {
        return Math.abs(i2 - i1);
    }
}

Utilities211Driver.java (Test Driver)

java

// Utilities211Driver.java
public class Utilities211Driver {
    public static void main(String[] args) {
        double d = -2.1;
        int x = 5;
        int y = -6;
        String s1 = " x ";
        String s2 = " cow ";
        Utilities211Code u = new Utilities211Code();

        System.out.println(u.validString(s1));   // false
        System.out.println(u.validString(s2));   // true
        System.out.println(u.numberSign(d));     // -1
        System.out.println(u.range(x, y));       // 11
    }
}

Expected Output

arduino

false
true
-1
11

How to Use:

Save each class in a separate .java file (as named above).

Compile:

nginx

javac Utilities211Interface.java
javac Utilities211Code.java
javac Utilities211Driver.java

Run the driver:
```
java Utilities211Driver
```

The answer

public abstract interface Utilities211Interface {

abstract boolean validString(String s);

abstract int numberSign(double d); abstract int range(int i1, int i2); }

import java.util.*;

public class Utilities211Code implements Utilities211Interface {

public boolean validString(String s){ s =s.replaceAll("\\s", "");

if(s.length() >=2 ) return true; else return false; }

public int numberSign(double d){

if(d >0) return 1; else if(d <0) return -1; else return 0; }

public int range(int i1, int i2){ int count =0; if(i1 > i2 ){

for(int i = i2 ; i <i1 ; i++ ){ count++; } return count; }

else{ for(int i = i1 ; i <i2 ; i++ ){ count++; } return count;

} } }

public class Utilities211Driver { public static void main(String[] args){

double d= −2.1 ; int x = 5; int y = −6; String s1 = "x ";

String s2 = "cow ";

Utilities211Code u = new Utilities211Code( );

System.out.println(u.validString(s1));

System.out.println(u.validString(s2));

System.out.println(u.numberSign( d ));

System.out.println(u.range( x,y ) ); } }

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Java Programming: Implementing and Testing a Custom Interface (Utilities211Interface Assignment)