java

Convert list to array in Java [duplicate]

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Either: Foo[] array = list.toArray(new Foo[0]); or: Foo[] array = new Foo[list.size()]; list.toArray(array); // fill the array Note that this works only for arrays of reference types. For arrays of primitive types, use the traditional way: List<Integer> list = …; int[] array = new int[list.size()]; for(int i = 0; i < list.size(); i++) array[i] = … Read more

Sending Email in Android using JavaMail API without using the default/built-in app

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Send e-mail in Android using the JavaMail API using Gmail authentication. Steps to create a sample Project: MailSenderActivity.java: public class MailSenderActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); final Button send = (Button) this.findViewById(R.id.send); send.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { try { GMailSender sender = new GMailSender(“username@gmail.com”, “password”); sender.sendMail(“This … Read more

Java: convert List to a join()d String

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String.join With Java 8 you can do this without any third party library. If you want to join a Collection of Strings you can use the String.join() method: List<String> list = Arrays.asList(“foo”, “bar”, “baz”); String joined = String.join(” and “, list); // “foo and bar and baz” Collectors.joining If you have a Collection with another … Read more

Why are static variables considered evil?

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Static variables represent global state. That’s hard to reason about and hard to test: if I create a new instance of an object, I can reason about its new state within tests. If I use code which is using static variables, it could be in any state – and anything could be modifying it. I … Read more

Ignoring new fields on JSON objects using Jackson [duplicate]

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Jackson provides an annotation that can be used on class level (JsonIgnoreProperties). Add the following to the top of your class (not to individual methods): @JsonIgnoreProperties(ignoreUnknown = true) public class Foo { … } Depending on the jackson version you are using you would have to use a different import in the current version it … Read more

How to check internet access on Android? InetAddress never times out

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If the device is in airplane mode (or presumably in other situations where there’s no available network), cm.getActiveNetworkInfo() will be null, so you need to add a null check. Modified (Eddie’s solution) below: public boolean isOnline() { ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); NetworkInfo netInfo = cm.getActiveNetworkInfo(); return netInfo != null && netInfo.isConnectedOrConnecting(); } Also add … Read more