Getting ArrayOutOfBound on Java 8

Question

I am working on a Spring MVC project and I am getting an ArrayOutOfBound exception. If this was Java 7 then I would have no problem, but since it's Java 8 and I am new to it, I have no idea what the problem is. I have searched for about two days but have no luck. I would appreciate the help.

Now the out of bounds is caused by ProjectService class and specifically the public Project find(Long projectId)....

Now my service class is:

import java.math.BigDecimal;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.stream.Collectors;
import org.springframework.stereotype.Service;
import com.spring.project.model.Project;

@Service
public class ProjectService {

    private List<Project> projects = new LinkedList<>();

    public ProjectService(){
        Project javaProject = this.createProject("Java Project", "This is a Java Project");
        Project javascriptProject = this.createProject("Javascript Project", "This is a Javascript Project");
        Project htmlProject = this.createProject("HTML Project", "This is an HTML project");

        this.projects.addAll(Arrays.asList(new Project[]{javaProject,javascriptProject, htmlProject}));
    }

    public List<Project> findAll(){
        return this.projects;
    }

    public Project find(Long projectId){
        return this.projects.stream().filter(p -> {
            return p.getProjectId().equals(projectId);
        }).collect(Collectors.toList()).get(0);
    }

    private Project createProject(String title, String description){
        Project project = new Project();

        project.setName(title);
        project.setAuthorizedFunds(new BigDecimal("100000"));
        project.setAuthorizedHours(new BigDecimal("1000"));
        project.setDescription(description);
        project.setSponsor("NASA");
        project.setYear("2016");
        project.setSpecial(true);
        project.setType("single");

        return project;

    }

}

Now my controller looks like this:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import com.spring.project.services.ProjectService;

@Controller
@RequestMapping("/project")
public class ProjectController {


    @Autowired
    private ProjectService projectService;

    @RequestMapping(value="/{projectId}")
    public String findProject(Model model, @PathVariable("projectId") Long projectId){
        model.addAttribute("project", this.projectService.find(projectId));
        return "project";
    }

    @RequestMapping(value="/find")
    public String find(Model model){
        model.addAttribute("projects", this.projectService.findAll());
        return "projects";
    }
}

You like redundant code, do you? Instead of `Arrays.asList(new Project[]{x,y,z})`, you can just write `Arrays.asList(x,y,z)` and`.filter(p -> { return p.getProjectId().equals(projectId); })`, can be replaced with `.filter(p -> p.getProjectId().equals(projectId))`. And if you are only interested in the first match, use `findFirst()` instead of collecting everything in a `List`. — Holger, Jul 01 '16 at 11:46

score 1 · Answer 1 · edited Sep 18 '16 at 16:45

1

Withouth a stack trace it's hard to tell, but this code fragment looks suspicious:

return this.projects.stream().filter(p -> {
    return p.getProjectId().equals(projectId);
}).collect(Collectors.toList()).get(0);

If method invocation collect(Collectors.toList()) returns an empty list, then getting the first element of the empty list will result in java.lang.IndexOutOfBoundsException. Consider using Streams#findFirst that returns Optional instead of collect(Collectors.toList()).get(0) that can throw exception.

edited Sep 18 '16 at 16:45

Nisse Engström

4,738
23
27
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answered Jun 30 '16 at 21:11

Tomasz Bekas

666
6
15

Of course, if the OP then unconditionally calls `get()` on the `Optional`, it won’t help. The key point is dealing with the possibility of not finding a match. But at least, `findFirst()` is more efficient. – Holger Jul 01 '16 at 11:48
That's true. I assumed that OP will read documentation and handle this case. – Tomasz Bekas Jul 01 '16 at 22:41

score 0 · Accepted Answer · edited Sep 18 '16 at 16:39

0

The problem is with the lambda expression in filter. Remove the return statement from the filter and try:

i.e. your code is very verbose and it should read as below:

return this.projects.stream().filter(p -> p.getProjectId().equals(projectId)).findFirst().get();

When you try to search an id that is not present you will get java.util.NoSuchElementException which is more meaningful. get(0) is the root cause of your java.lang.IndexOutOfBoundsException.

edited Sep 18 '16 at 16:39

Nisse Engström

4,738
23
27
42

answered Jul 01 '16 at 12:22

Naresh Kumar

673
7
17

As @Holger explained, invocation of `get()` on empty Optional will result in NoSuchElementException. You should either use `orElse`/`orElseGet` method or check the presence with the `isPresent()` and if present then you can safely call `get()`. – Tomasz Bekas Jul 01 '16 at 22:46

Getting ArrayOutOfBound on Java 8

2 Answers2