Returning a String converted to Unicode in Java

I am taking a Java course and I am stumped on this question. I was to complete most of it up until the portion where I am required to convert a String to ASCII. I am able to get the first letter to output to Edit Unicode but it stops there. When I isolate the code on a scratch file and use a print statement it prints how it should:

class Scratch {
public static void main(String[] args) {
String str = "yams";
for (int i = 0; i < str.length(); i++) {
int numUni = (int)str.charAt(i);
int unicode = (int)numUni;
System.out.print(unicode + " ");
//return unicode; //  this line will need to be changed
}
}

}

Output:

121 97 109 115 
Process finished with exit code 0

Here is the code that I have completed so far and my issue is with Step 4:

public class Strings{
// STEP one - concatenateStrings()
public String concatenateStrings(String word1, String word2){
String concantWord = word1 + " " + word2;
return concantWord;
}
// STEP two - charToASCII()
public int charToASCII(char character){
int convertedChar = character;
return convertedChar;
}
// STEP three
public char getLastChar(String str){
//student code here\
int strLength = str.length();
char lastChar = str.charAt(str.length() - 1);
return lastChar; //  this line will need to be changed
}
// step 4
public static String translateWord(String str){
//student code here
for (int i = 0; i < str.length(); i++) {
int numUni = (int)str.charAt(i);
String unicode = numUni + " ";
return unicode; //  this line will need to be changed
}
return "";
}
// step 5
public String madLib(String noun1, double number, String pastTenseVerb, String adjective, String noun2) {
//student code here
return ""; // this line will need to be changed
}
/**
* A test block helps you test as you write. Eventually, you will learn
* test driven development, in which every method you write will have tests you write
* to make sure it works.
*
* Uncomment these lines out as you finish your various methods
*/
public void runTests() {
System.out.println();
//Concatenate Strings test
System.out.println("Testing concatenateStrings method: ");
System.out.println("Input: 'good','morning' \t Expecting: good morning\t Actual: " + concatenateStrings("good", "morning"));
System.out.println();
//Char to ASCII test
System.out.println("Testing charToASCII method: ");
System.out.println("Input: 'c' \t Expecting: 99\t Actual:" + charToASCII('c'));
System.out.println();
//Get Last Char test
System.out.println("Testing getLastChar method: ");
System.out.println("Input: 'Pterodactyl' \t Expecting: L\t Actual: " + getLastChar("Pterodactyl"));
System.out.println();
//Translate Word Test
System.out.println("Testing Translate word method: ");
System.out.println("Input: 'yams' \t Expecting: 121 97 109 115\t Actual: " + translateWord("yams"));
// System.out.println();
// Mad Libs Test
// System.out.println("Testing Mad Libs method: ");
// System.out.println("Input: 'pear, 202.356, swam, purple, bear'"
//      + "\nExpecting: Today I went to the store and bought a pear for $202.36.\nThen I swam and saw a purple bear."
//      + "\nActual: " + madLib("pear", 202.356, "swam", "purple", "bear"));
}
public static void main(String [] args) {
// running test method
Strings f = new Strings();
f.runTests();  // this is not a static method (should it have been?) so you have to run it with the object
}

}

I would appreciate any guidance.

Obviously, if you return inside a loop, the loop will only ever execute once.

You want to 'build up' your string, one ascii code at a time (well, unicode codepoint, really - as others have pointed out, I don't know what dank late 80s outdated cruft you're following, mate - the days of ASCII are loooong gone), so you need a StringBuilder, you want to append 'numUni + " "' to this in the loop, and then return the stringbuilder, built up to a string:

StringBuilder out = new StringBuilder();
for (int i = 0; i < str.length(); i++) {
int uni = (int) str.charAt(i);
out.append(uni).append(" ");
}
return out.toString();

You're returning the ascii value immediately after the first iteration, edit your code to look something like below:

public static String translateWord(String str) {
//student code here
String ascii = "";
for (int i = 0; i < str.length(); i++) {
int numascii = str.charAt(i);
ascii += numascii + " ";
}
return ascii;
}

edit: As mentioned by commenter below, definitely read about String pool, StringBuilder and StringBuffer