// Create a COSClient instance, which is used to initiate requests later.
COSClient createCOSClient() {
    // Set the user identity information.
    // Log in to the [CAM console](https://console.tencentcloud.com/cam/capi) to view and manage the `SecretId` and `SecretKey` of your project.
    String secretId = "SECRETID";
    String secretKey = "SECRETKEY";
    COSCredentials cred = new BasicCOSCredentials(secretId, secretKey);

    // `ClientConfig` contains the COS client configuration for subsequent COS requests.
    ClientConfig clientConfig = new ClientConfig();

    // Set the bucket region.
    // For more information on COS regions, please visit https://www.tencentcloud.com/document/product/436/6224.
    clientConfig.setRegion(new Region("COS_REGION"));

    // Set the request protocol, `http` or `https`.
    // For 5.6.53 and earlier versions, HTTPS is recommended.
    // Starting from 5.6.54, HTTPS is used by default.
    clientConfig.setHttpProtocol(HttpProtocol.https);

    // The following settings are optional.

    // Set the read timeout period, which is 30s by default.
    clientConfig.setSocketTimeout(30*1000);
    // Set the connection timeout period, which is 30s by default.
    clientConfig.setConnectionTimeout(30*1000);

    // If necessary, set the HTTP proxy, IP, and port.
    clientConfig.setHttpProxyIp("httpProxyIp");
    clientConfig.setHttpProxyPort(80);

    // Generate a COS client.
    return new COSClient(cred, clientConfig);
}


// Create a COSClient instance, which is used to initiate requests later.
COSClient createCOSClient() {
    // Here, the temporary key information is needed.
    // For how to generate temporary keys, please visit https://www.tencentcloud.com/document/product/436/14048.
    String tmpSecretId = "TMPSECRETID";
    String tmpSecretKey = "TMPSECRETKEY";
    String sessionToken = "SESSIONTOKEN";

    COSCredentials cred = new BasicSessionCredentials(tmpSecretId, tmpSecretKey, sessionToken);

    // `ClientConfig` contains the COS client configuration for subsequent COS requests.
    ClientConfig clientConfig = new ClientConfig();

    // Set the bucket region.
    // For more information on COS regions, please visit https://www.tencentcloud.com/document/product/436/6224.
    clientConfig.setRegion(new Region("COS_REGION"));

    // Set the request protocol, `http` or `https`.
    // For 5.6.53 and earlier versions, HTTPS is recommended.
    // Starting from 5.6.54, HTTPS is used by default.
    clientConfig.setHttpProtocol(HttpProtocol.https);

    // The following settings are optional.

    // Set the read timeout period, which is 30s by default.
    clientConfig.setSocketTimeout(30*1000);
    // Set the connection timeout period, which is 30s by default.
    clientConfig.setConnectionTimeout(30*1000);

    // If necessary, set the HTTP proxy, IP, and port.
    clientConfig.setHttpProxyIp("httpProxyIp");
    clientConfig.setHttpProxyPort(80);

    // Generate a COS client.
    return new COSClient(cred, clientConfig);
}

public boolean doesObjectExist(String bucketName, String key)
            throws CosClientException, CosServiceException;

// Before using the COS API, ensure that the process contains a COSClient instance. If such an instance does not exist, create one.
// For the detailed code, see "Simple Operations -> Creating a COSClient instance" on the current page.
COSClient cosClient = createCOSClient();

// Enter the bucket name in the format of `BucketName-APPID`.
String bucketName = "examplebucket-1250000000";
// Object key, the unique ID of an object in a bucket. For more information, please see [Object Key](https://www.tencentcloud.com/document/product/436/13324).
String key = "exampleobject";

try {
    boolean objectExists = cosClient.doesObjectExist(bucketName, key);
} catch (CosServiceException e) {
    e.printStackTrace();
} catch (CosClientException e) {
    e.printStackTrace();
}

// After confirming that the process does not use the COSClient instance anymore, close it.
cosClient.shutdown();