# createIndex()

This operation creates an index for a specific collection.

```java
public void createIndex(CreateIndexReq request)
```

## Request Syntax

```java
createIndex(CreateIndexReq.builder()
    .databaseName(String databaseName)
    .collectionName(String collectionName)
    .indexParams(List<IndexParam> indexParams)
    .sync(Boolean sync)
    .timeout(Long timeout)
    .build()
);
```

**BUILDER METHODS:**

- `databaseName(String databaseName)` -

    The name of the database. Defaults to the current database if not specified.

- `collectionName(String collectionName)` -

    The name of the target collection.

- `indexParams(List<IndexParam> indexParams)` -

    A list of IndexParam objects defining the index configuration.

- `sync(Boolean sync)` -

    Whether to wait synchronously until the operation completes. Defaults to `Boolean.TRUE`.

- `timeout(Long timeout)` -

    The timeout duration in milliseconds. Defaults to `60000L`.

**RETURNS:**

*void*

**EXCEPTIONS:**

- **MilvusClientException**

    This exception will be raised when any error occurs during this operation.

## Example

```java
import io.milvus.v2.client.ConnectConfig;
import io.milvus.v2.client.MilvusClientV2;
import io.milvus.v2.common.IndexParam;
import io.milvus.v2.service.index.request.CreateIndexReq;

// 1. Set up a client
ConnectConfig connectConfig = ConnectConfig.builder()
        .uri("http://localhost:19530")
        .token("root:Milvus")
        .build();
        
MilvusClientV2 client = new MilvusClientV2(connectConfig);

// 2. Create an index for the field "vector"
IndexParam indexParam = IndexParam.builder()
        .metricType(IndexParam.MetricType.L2)
        .indexType(IndexParam.IndexType.AUTOINDEX)
        .fieldName("vector")
        .build();
CreateIndexReq createIndexReq = CreateIndexReq.builder()
        .collectionName("test")
        .indexParams(Collections.singletonList(indexParam))
        .build();
client.createIndex(createIndexReq);
```