颜色识别器：识别字符串中的红色或蓝色

Question

So basically I have to take these words as an input or hard coded(doesn't really matter). And I have to print what color the word has for example. "Red Dogs"-->Red. And I have two colors red and blue. When its neither I get an extra empty string.

    Scanner input=new Scanner(System.in);
    String h=System.out.println("Enter a word");
    String i=input.next();




public static String color(str r, str b){
    for(int i=0;i<=h.length;i++){
      if(i="red"){
        System.out.println("Red");
      }else if(i="blue"){
        System.out.println("Blue");
      }else{
        return("");
  }
}

}

Answer 1

practice more.

public static void main(String[] args) {

    String colorStr = "RED DOG BLUE BIRD";
    System.out.println(color(colorStr));
}

public static String color(String colorStr) {

    Set<String> set = new HashSet<>(Arrays.asList("RED", "BLUE"));
    StringBuilder presentColorStr = new StringBuilder();

    String[] words = colorStr.split(" ");

    for (String word : words) {
        if(set.contains(word)) {
            presentColorStr.append(word).append(" ");
        }
    }

    return presentColorStr.toString();
}

Answer 2

Looks like you are entirely new to Java code. I will explain few things about your code.

1. Conditinal construct if..else accept a boolean literal only.

   if(a = b) // this is error as = is assignment operator and will not return boolean unless you assign a boolean

   if(a == b) // this is right approach to compare two values.

2. Comparison of two reference is different than values. Ex. String holds reference so you cannot compare two string with ==. You must compare two Strings with equals method that returns boolean if both string are same.

   String str1 = "hello"; String str2 = "hello";

   if(str1.equals(str2)) { System.out.println("both are same."); }

Further, your requirement to check if input string contains a string can be done using String.contains() function

String str1 = "Red Ball";
String str2 = "ball";
    
if(str1.contains(str2)) {
  System.out.println("String conatins str2");
}

You can also use methods toLowerCase() and toUpperCase() to make it case independent.