ProxySelector select(URI) in Java

select(URI): This method is available in the java.net.ProxySelector class of Java.

Syntax:

List<Proxy> java.net.ProxySelector.select(URI uri)

This method takes one argument. This method selects all the applicable proxies based on the protocol to access the resource with and a destination address to access the resource at.

The format of the URI is defined as follows:

1. http URI for http connections.

2. https URI for https connections.

3. socket://host:port for tcp client socket connections.

Parameters: One parameter is required for this method.

uri: The URI that a connection is required to.

Returns: a List of Proxies. Each element in the List is of type Proxy; when no proxy is available, the list will contain one element of type Proxy that represents a direct connection.

Throws:

1. IllegalArgumentException - if the argument is null or if the protocol or host cannot be determined from the provided uri

Approach 1: When no exception

Java

package com.ProxySelector;

import java.net.ProxySelector;
import java.net.URI;
import java.net.URISyntaxException;

public class ProxySelectorselect {
    public static void main(String[] args) throws URISyntaxException {
        ProxySelector proxySelector = ProxySelector.getDefault();

        URI uri = new URI("http://localhost:8080");
        proxySelector.select(uri);
        System.out.println("Successfully select");
    }
}

Output:

Successfully select

Approach 2: IllegalArgumentException 

Java

package com.ProxySelector;

import java.net.ProxySelector;
import java.net.URI;
import java.net.URISyntaxException;

public class ProxySelectorselect {
    public static void main(String[] args) throws URISyntaxException {
        ProxySelector proxySelector = ProxySelector.getDefault();

        URI uri = null;
        proxySelector.select(uri);
        System.out.println("Successfully select");
    }
}

Output:

Exception in thread "main" java.lang.IllegalArgumentException: URI can't be null.
	at java.base/sun.net.spi.DefaultProxySelector.select(DefaultProxySelector.java:155)
	at com.ProxySelector.ProxySelectorselect.main(ProxySelectorselect.java:12)

Some other methods of ProxySelector class

connectFailed(URI, SocketAddress, IOException): This method is called to indicate that a connection could not be established to a proxy/socks server.

getDefault(): This method gets the system-wide proxy selector.

ProxySelector.of(InetSocketAddress):  This method returns a ProxySelector which uses the given proxy address for all HTTP and HTTPS requests. If the proxy is null then proxying is disabled.

select(URI): This method selects all the applicable proxies based on the protocol to access the resource with and a destination address to access the resource at.

ProxySelector.setDefault(ProxySelector): This method sets (or unsets) the system-wide proxy selector.