How to find the location of a specific String in my array? [duplicate]

You could use Arrays.asList to create a List from the array and use the indexOf method.

final List<String> planetList = Arrays.asList(verifyPlanet);
int index = planetList.indexOf("Mercury");//0

The more efficient, albeit less convenient, way would be to implement your own indexOf method for a String array.

public static void main(final String[] args) {
    final String[] verifyPlanet = { "Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune" };
    System.out.println(indexOf(verifyPlanet, "Mercury"));//0
}

private static int indexOf(final String[] arr, final String search) {
    for (int i = 0, len = arr.length; i < len; i++) {
        if (arr[i].equals(search)) {
            return i;
        }
    }
    return -1;
}

First check if lets say "Earth" is in the array or not:

String planetName = "Earth";
for(String str: verifyPlanet){
     if(str.equals(planetName)){
         for(int i=0;i < verifyPlanet.length;i++){
             if(verifyPlanet[i] == "Earth"){
                 double diameter = (double)Array.get(getDiameter, i);
}}}}

This is the most basic way to do this. Other ways exist to reduce this code to. Can use indexOf() method to get value too. But if your application is not too big, then it is simple and easy to understand.