A simple example of HashTable in Java

HashTable.java

import java.util.Scanner;

class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        HashTable<String> table = new HashTable<>(Integer.parseInt(sc.nextLine()));

        while (sc.hasNext()) {
            String[] inputArr = sc.nextLine().split(" ");
            switch (inputArr[0]) {
                case "put" :
                    table.put(Integer.parseInt(inputArr[1]), inputArr[2]);
                    break;
                case "get" :
                    System.out.println(table.get(Integer.parseInt(inputArr[1])));
                    break;
                case "remove" :
                    table.remove(Integer.parseInt(inputArr[1]));
                    break;
            }
        }
    }

    private static class TableEntry<T> {

        private final int key;
        private final T value;
        private boolean removed;

        public TableEntry(int key, T value) {
            this.key = key;
            this.value = value;
        }

        public int getKey() {
            return key;
        }

        public T getValue() {
            return value;
        }

        public void remove() {
            removed = true;
        }

        public boolean isRemoved() {
            return removed;
        }
    }

    private static class HashTable<T> {
        private int size;
        private TableEntry[] table;

        public HashTable(int size) {
            this.size = size;
            table = new TableEntry[size];
        }

        public boolean put(int key, T value) {
            int index = findKey(key);

            if (index == -1) return false;

            table[index] = new TableEntry(key, value);
            return true;
        }

        public T get(int key) {
            int index = findKey(key);

            if (index == -1 || table[index] == null) return (T) "-1";

            return (T) table[index].getValue();
        }

        public void remove(int key) {
            int index = findKey(key);

            if (table[index] != null) {
                table[index].remove();
                table[index] = new TableEntry(key, "-1");
            }
        }
        
        private int findKey(int key) {
            int hash = key % size;

            // loop through table looking for empty index (hash)
            while (!(table[hash] == null || table[hash].getKey() == key)) { // while not null (empty) bucket/
                                                                            // hash already index for correct key
                hash = (hash + 1) % size;

                // if we are at the end of the table size return false?
                if (hash == key % size || table[hash].isRemoved()) { // we've gone through all values of modulus 
                                                                    // and are back at the original hash
                    return -1;
                }
            }

            return hash;
        }

        @Override
        public String toString() {
            StringBuilder tableBuilder = new StringBuilder();
            int i = 0;
            try {
                for (i = 0; i < table.length; i++) {
                    if (table[i] != null) {
                        tableBuilder.append(String.format("index %d: Key= %d Value= %s \n", i,
                                table[i].getKey(),
                                table[i].getValue()));
                    }
                }
            } catch (Exception e) {
                e.printStackTrace();
                System.out.println("i: " + i);
            }
            return tableBuilder.toString();
        }
    }

}