# Invoke, list, and delete AWS Lambda functions
This section provides examples of programming with the Lambda service client by using the AWS SDK for Java 2.x.
**Topics**
+ [Invoke a Lambda function](#invoke-function)
+ [List Lambda functions](#list-function)
+ [Delete a Lambda function](#delete-function)
## Invoke a Lambda function
You can invoke a Lambda function by creating a [https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/lambda/LambdaClient.html](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/lambda/LambdaClient.html) object and invoking its `invoke` method. Create an [https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/lambda/model/InvokeRequest.html](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/lambda/model/InvokeRequest.html) object to specify additional information such as the function name and the payload to pass to the Lambda function. Function names appear as *arn:aws:lambda:us-east-1:123456789012:function:HelloFunction*. You can retrieve the value by looking at the function in the AWS Management Console.
To pass payload data to a function, create a [https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/core/SdkBytes.html](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/core/SdkBytes.html) object that contains information. For example, in the following code example, notice the JSON data passed to the Lambda function.
**Imports**
```
import software.amazon.awssdk.services.lambda.LambdaClient;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.lambda.model.InvokeRequest;
import software.amazon.awssdk.core.SdkBytes;
import software.amazon.awssdk.services.lambda.model.InvokeResponse;
import software.amazon.awssdk.services.lambda.model.LambdaException;
```
**Code**
The following code example demonstrates how to invoke a Lambda function.
```
public static void invokeFunction(LambdaClient awsLambda, String functionName) {
InvokeResponse res = null ;
try {
//Need a SdkBytes instance for the payload
String json = "{\"Hello \":\"Paris\"}";
SdkBytes payload = SdkBytes.fromUtf8String(json) ;
//Setup an InvokeRequest
InvokeRequest request = InvokeRequest.builder()
.functionName(functionName)
.payload(payload)
.build();
res = awsLambda.invoke(request);
String value = res.payload().asUtf8String() ;
System.out.println(value);
} catch(LambdaException e) {
System.err.println(e.getMessage());
System.exit(1);
}
}
```
See the [complete example](https://github.com/awsdocs/aws-doc-sdk-examples/blob/f807d60010caf3d14fe4cd0801b842fb8e9511ca/javav2/example_code/lambda/src/main/java/com/example/lambda/LambdaInvoke.java) on GitHub.
## List Lambda functions
Build a `[LambdaClient](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/lambda/LambdaClient.html)` object and invoke its `listFunctions` method. This method returns a [https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/lambda/model/ListFunctionsResponse.html](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/lambda/model/ListFunctionsResponse.html) object. You can invoke this object’s `functions` method to return a list of [https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/lambda/model/FunctionConfiguration.html](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/lambda/model/FunctionConfiguration.html) objects. You can iterate through the list to retrieve information about the functions. For example, the following Java code example shows how to get each function name.
**Imports**
```
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.lambda.LambdaClient;
import software.amazon.awssdk.services.lambda.model.LambdaException;
import software.amazon.awssdk.services.lambda.model.ListFunctionsResponse;
import software.amazon.awssdk.services.lambda.model.FunctionConfiguration;
import java.util.List;
```
**Code**
The following Java code example demonstrates how to retrieve a list of function names.
```
public static void listFunctions(LambdaClient awsLambda) {
try {
ListFunctionsResponse functionResult = awsLambda.listFunctions();
List list = functionResult.functions();
for (FunctionConfiguration config: list) {
System.out.println("The function name is "+config.functionName());
}
} catch(LambdaException e) {
System.err.println(e.getMessage());
System.exit(1);
}
}
```
See the [complete example](https://github.com/awsdocs/aws-doc-sdk-examples/blob/f807d60010caf3d14fe4cd0801b842fb8e9511ca/javav2/example_code/lambda/src/main/java/com/example/lambda/ListLambdaFunctions.java) on GitHub.
## Delete a Lambda function
Build a [https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/lambda/LambdaClient.html](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/lambda/LambdaClient.html) object and invoke its `deleteFunction` method. Create a [https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/lambda/model/DeleteFunctionRequest.html](https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/lambda/model/DeleteFunctionRequest.html) object and pass it to the `deleteFunction` method. This object contains information such as the name of the function to delete. Function names appear as *arn:aws:lambda:us-east-1:123456789012:function:HelloFunction*. You can retrieve the value by looking at the function in the AWS Management Console.
**Imports**
```
import software.amazon.awssdk.services.lambda.LambdaClient;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.lambda.model.DeleteFunctionRequest;
import software.amazon.awssdk.services.lambda.model.LambdaException;
```
**Code**
The following Java code demonstrates how to delete a Lambda function.
```
public static void deleteLambdaFunction(LambdaClient awsLambda, String functionName ) {
try {
DeleteFunctionRequest request = DeleteFunctionRequest.builder()
.functionName(functionName)
.build();
awsLambda.deleteFunction(request);
System.out.println("The "+functionName +" function was deleted");
} catch(LambdaException e) {
System.err.println(e.getMessage());
System.exit(1);
}
}
```
See the [complete example](https://github.com/awsdocs/aws-doc-sdk-examples/blob/f807d60010caf3d14fe4cd0801b842fb8e9511ca/javav2/example_code/lambda/src/main/java/com/example/lambda/DeleteFunction.java) on GitHub.