Gson: Convert json to a typed array list

Using TypeToken, you can convert a json to typed array list.

Example

Type type = new TypeToken<List<Employee>>() {}.getType();

List<Employee> deserializedEmps = gson.fromJson(json, type);

Employee.java

package com.sample.app.model;

public class Employee {
 private int id;

 private String firstName;
 private String lastName;

 public Employee() {

 }

 public Employee(int id, String firstName, String lastName) {
  super();
  this.id = id;
  this.firstName = firstName;
  this.lastName = lastName;
 }

 public int getId() {
  return id;
 }

 public void setId(int id) {
  this.id = id;
 }

 public String getFirstName() {
  return firstName;
 }

 public void setFirstName(String firstName) {
  this.firstName = firstName;
 }

 public String getLastName() {
  return lastName;
 }

 public void setLastName(String lastName) {
  this.lastName = lastName;
 }

 @Override
 public String toString() {
  return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + "]";
 }

}

App.java

package com.sample.app;

import java.util.Arrays;
import java.util.List;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.sample.app.model.Employee;
import java.lang.reflect.Type;
import com.google.gson.reflect.TypeToken;

public class App {

 public static void main(String args[]) throws ClassNotFoundException {
  Employee emp1 = new Employee(1, "Ravindra", "Gidugu");
  Employee emp2 = new Employee(2, "Rahim", "Khan");
  Employee emp3 = new Employee(3, "Joel", "Chelli");
  Employee emp4 = new Employee(4, "Ram", "Gurram");

  List<Employee> emps = Arrays.asList(emp1, emp2, emp3, emp4);

  Gson gson = new GsonBuilder().setPrettyPrinting().create();

  String json = gson.toJson(emps);

  Type type = new TypeToken<List<Employee>>() {}.getType();

  List<Employee> deserializedEmps = gson.fromJson(json, type);

  for (Employee emp : deserializedEmps) {
   System.out.println(emp);
  }
 }
}

Output

Employee [id=1, firstName=Ravindra, lastName=Gidugu]

Employee [id=2, firstName=Rahim, lastName=Khan]

Employee [id=3, firstName=Joel, lastName=Chelli]

Employee [id=4, firstName=Ram, lastName=Gurram]

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Shuffle array lists in same fashion (java)

Using Collections.shuffle

By passing randomizer with same seed to Collections.shuffle function, you can shuffle array lists in same fashion.

App.java

package com.sample.app;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Random;

public class App {

 private static void printList(List list) {
  for (Object obj : list) {
   System.out.print(obj + " ");
  }
  System.out.println();
 }

 public static void main(String args[]) {
  List<Integer> ids = Arrays.asList(1, 2, 3, 4, 5);
  List<Character> chars = Arrays.asList('a', 'b', 'c', 'd', 'e');

  long seed = System.currentTimeMillis();

  Random rand1 = new Random(seed);
  Random rand2 = new Random(seed);

  Collections.shuffle(ids, rand1);
  Collections.shuffle(chars, rand2);

  printList(ids);
  printList(chars);

 }
}

Output

2 4 3 1 5

b d c a e

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