How to Crack Java Programming Interviews Without Experience

public class CoreJavaDemo {
    public static void main(String[] args) {
        String a = "java";
        String b = "java";
        String c = new String("java");

        System.out.println(a == b);       // true  (same pooled literal)
        System.out.println(a == c);       // false (different object)
        System.out.println(a.equals(c));  // true  (same content)

        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < 3; i++) {
            sb.append(i).append(',');
        }
        System.out.println(sb);           // 0,1,2,
    }
}

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class ReadFirstLine {
    public static void main(String[] args) {
        // try-with-resources closes the reader automatically
        try (BufferedReader br = new BufferedReader(new FileReader("data.txt"))) {
            System.out.println(br.readLine());
        } catch (IOException e) {          // checked exception
            System.out.println("Could not read file: " + e.getMessage());
        }

        int[] nums = {1, 2, 3};
        try {
            System.out.println(nums[5]);   // unchecked exception
        } catch (ArrayIndexOutOfBoundsException e) {
            System.out.println("Index problem: " + e.getMessage());
        }
    }
}

interface Shape {
    double area();
}

class Circle implements Shape {
    private final double r;
    Circle(double r) { this.r = r; }
    public double area() { return Math.PI * r * r; }
}

class Rectangle implements Shape {
    private final double w, h;
    Rectangle(double w, double h) { this.w = w; this.h = h; }
    public double area() { return w * h; }
}

public class Shapes {
    public static void main(String[] args) {
        Shape[] shapes = { new Circle(1), new Rectangle(2, 3) };
        for (Shape s : shapes) {
            System.out.printf("%.2f%n", s.area());
        }
    }
}

public class BankAccount {
    private double balance;   // hidden from outside

    public void deposit(double amount) {
        if (amount <= 0) {
            throw new IllegalArgumentException("Amount must be positive");
        }
        balance += amount;
    }

    public boolean withdraw(double amount) {
        if (amount > 0 && amount <= balance) {
            balance -= amount;
            return true;
        }
        return false;
    }

    public double getBalance() { return balance; }
}

import java.util.HashMap;
import java.util.Map;

public class CodingRound {
    // First non-repeating character in a string
    static char firstUnique(String s) {
        Map<Character, Integer> count = new HashMap<>();
        for (char ch : s.toCharArray()) {
            count.merge(ch, 1, Integer::sum);
        }
        for (char ch : s.toCharArray()) {
            if (count.get(ch) == 1) return ch;
        }
        return '_';
    }

    public static void main(String[] args) {
        System.out.println(firstUnique("swiss"));   // w
    }
}

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class StreamDemo {
    public static void main(String[] args) {
        List<String> names = Arrays.asList("Asha", "Ravi", "Anil", "Meera");

        List<String> aNames = names.stream()
                .filter(n -> n.startsWith("A"))
                .map(String::toUpperCase)
                .sorted()
                .collect(Collectors.toList());

        System.out.println(aNames);   // [ANIL, ASHA]
    }
}

Topic                         | Can explain? | Example ready? | Revised on
------------------------------|--------------|----------------|-----------
JDK / JRE / JVM               |              |                |
OOP four pillars              |              |                |
Overloading vs overriding     |              |                |
String, StringBuilder         |              |                |
Exceptions                    |              |                |
Collections hierarchy         |              |                |
HashMap internals             |              |                |
equals() and hashCode()       |              |                |
Multithreading basics         |              |                |
Java 8 streams and lambdas    |              |                |

Date | Problem | Java concepts used | Time | Solved alone? | Notes
-----|---------|--------------------|------|---------------|------
     |         |                    |      |               |
     |         |                    |      |               |

Daily target: 2 problems in Java
Weekly: 1 timed set of 3 problems in 60 minutes

Project talking points (for 'Tell me about your project')

Project name: ____________
Problem it solves: ________
Java features used: OOP / collections / JDBC / exceptions
Hardest bug and fix: _______
What I would improve: ______
GitHub link: ______________

Practise saying this in under 90 seconds.