Returning a string that begins at the input parameter index of the String

The Method name is getTheString()

The Return type is String

And the Input parameters is int

I have to return a string that begins at input parameter index position of the String str which is the instance variable. Returns empty string if the input parameter index position is larger than or equal to the string length.

An example would be

If str = “Hawaii”

getTheString(8) returns “ “

getTheString(2) returns
“waii”

I don't know why nothing happens when I execute it or how to fix it could someone help.

public class LoopM
{
   public int a, b;
   public String str;
   
   public LoopM(){
    }
   
   public String getTheString(int f){
       
       str = "Hawaii";
       
       int length = str.length();
       
       for(f = length; f < 10; f++){
           
           return str.substring(f);
        }
       
       return str.substring(f);
    }
   
   public static void main(String args[]){
       //used for testing

       LoopM me = new LoopM();
       me.getTheString(2);
      
    }
}

Update to this :

public class Test {
	public static void main(String[] args) {
		System.out.println(getTheString(2));
	}

	public static String getTheString(int f) {

		String str = "Hawaii";

		return (f > str.length() || f < 0) ? "" : str.substring(f);
	}

}

Output :

waii

You should be using constructor to set value of str field instead of hardcoding it inside getTheString method, also the loop with the return statement inside is a bit strange.

Also you should check if the input parameters are valid (i.e., if str is not null and that f is not negative and less than str.length()

Thus, the code may be improved as follows:

public class LoopM {
    public int a, b;
    public String str;

    public LoopM() {
        this("Hawaii");
    }

    public LoopM(String str) {
        this.str = str;
    }
   
   public String getTheString(int f) {
       
       int length = null == str? -1 : str.length();
       
       return f > -1 && f < length ? str.substring(f) : "";
    }
   
   public static void main(String args[]){
       //used for testing

       LoopM me = new LoopM();
       System.out.printf("\"%s\"%n", me.getTheString(2));  // prints "waii"
       System.out.printf("\"%s\"%n", me.getTheString(10));  // prints ""
    }
}

The return statement consists of a ternary condition similar to if-else conditions. If the index is greater than the length of the string than it will return " " else it will return substring from the input index

public class Test {
    public static void main(String[] args) {
        System.out.println("String that begins at 2 index : "+getTheString(2)); // Output waii
        System.out.println("String that begins at 8 index : "+getTheString(8));// Output ""
    }

    public static String getTheString(int index) {

        String str = "Hawaii";

        return index > str.length() ? "" : str.substring(index);
    }

}