An introduction to Kubernetes, the open-source container orchestration system developed by Google

Kubernetes is an open-source container orchestration system that was developed by Google. It can be used to manage containerized applications across a cluster of machines. It automates the deployment, scaling, and management of containerized applications.

To use Kubernetes on Google Cloud, you can use Google Kubernetes Engine (GKE) which allows you to easily create and manage a Kubernetes cluster on Google Cloud.

An example of how to use Kubernetes to manage a Java application on Google Cloud would be to first package your Java application in a Docker container.
You can use a Dockerfile to create the container image, for example:

FROM openjdk:8
COPY . /app
WORKDIR /app
RUN javac Main.java
CMD ["java", "Main"]

You can then create a Kubernetes Deployment to manage the containerized application, for example:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-java-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-java-app
  template:
    metadata:
      labels:
        app: my-java-app
    spec:
      containers:
      - name: my-java-app
        image: gcr.io/my-project/my-java-app:v1
        ports:
        - containerPort: 8080

and a Service to define how the application can be accessed, for example:

apiVersion: v1
kind: Service
metadata:
  name: my-java-app
spec:
  selector:
    app: my-java-app
  ports:
  - name: http
    port: 80
    targetPort: 8080
  type: LoadBalancer

You can also use Kubernetes ConfigMap and Secrets to manage application configuration and secrets separately from your application code, as well as use Kubernetes resource like pod, service and replica set to control how your application is deployed and scaled.

You can use command-line tools such as 'kubectl' to interact with your Kubernetes cluster and deploy your application.

kubectl apply -f deployment.yml
kubectl apply -f service.yml

Please note that the above code examples are just a simple demonstration of how to use Kubernetes on GCP with a Java application, and a complete implementation will likely require additional configuration and resources.