stream every records based on filter and put them in list of errors-CodePudding

I am new to Java streams. I need to iterate over a list of objects and populate my list of errors based on my comparisons. I want to avoid using if else and use java stream. Is there a way I can do this?

public void compare(List<Tool> tools,Tool temp,List<String> error){
for(Tool t : tools){
   if(!t.name.equals(temp.name() && !t.id.equals(temp.id())
    errors.add(name id "not matches");
   if(!t.name.equals(temp.name())
    errors.add(name "not matches");
   else if(!t.id.equals(temp.id())
    errors.add(id "not matched");
}

class Tool{
  String name;
  String id;
}

CodePudding user response：

Unfortunately you need your if-else statements in this case. The stream approach would look something like this:

tools
        .stream()
        .filter(tool -> !tool.name.equals(temp.name) && !tool.id.equals(temp.id))
        .forEach(tool -> {
            errors.add(name id "not matches");  
        });

tools
        .stream()
        .filter(tool -> !tool.name.equals(temp.name))
        .forEach(tool -> {
            errors.add(name "not matches");   
        });

by this approach the exclusion of having only "errors.add(name id "not matches");" and not also "errors.add(name "not matches");" in your errors list would be gone.

The correct approach using streams therefore would look quite similar to your original implementation

        tools.forEach(tool -> {
            if (!tool.name.equals(temp.name) && !tool.id.equals(temp.id)) {
                errors.add(name   id   "not matches");
            } else if (!tool.name.equals(temp.name)) {
                errors.add(name   "not matches");
            } else if (!tool.id.equals(temp.id)) {
                errors.add(id   "not matched");
            }
        });

CodePudding user response：

The filter is id or name being different. All error messages can be constructed using 1 expression by using ternaries, so you can map non matching tools to a message in one step:

public void compare(List<Tool> tools, Tool temp, List<String> error) {
    tools.stream()
      .filter(t -> !t.id.equals(tool.id) || !t.name.equals(tool.name))
      .map(t -> (t.name.equals(tool.name) ? "" : name)   (t.id.equals(tool.id) ? "" : id)   "not matches")
      .forEach(error::add);
}