如何在Java中为单词分配数字？

Question

I have a problem about the last part of the code. I want to assign numbers to specific words but i always get 0 value, even though I get those strings from the first System.out.println correctly, i cannot get the numerical equivalents of those strings at the second System.out.println.Any ideas how to solve this problem?

public static double number;

protected void myMethod(HttpServletRequest request, HttpServletResponse response) {

    String speech= request.getParameter("speech");
    System.out.println("The recognized speech is : "+ speech);

    // There is no problem till here.
    if(speech == "Hi")
        number = 1 ;
    if(speech== "Thanks")
        number = 2 ;
    if(speech== "Bye")
        number = 0 ;

    System.out.println("The number for the speech is : " + number);
}

However here i dont get the correct numbers but only 0 for each word!

Answer 1

The == will only be true if the Strings are the same object. Use:

if(speech.equals("Hi"))

or to match without case:

if(speech.equalsIgnoreCase("hi"))

Answer 2

You can't use the == operator to check if two Strings have the same value in Java, you need to use the .equals() or equalsIgnoreCase() methods instead:

if("Hi".equalsIgnoreCase(speech)) {
    number = 1;
}
else if("Thanks".equalsIgnoreCase(speech)) {
    number = 2;
}
else if("Bye".equalsIgnoreCase(speech)) {
    number = 0;
}
else {
    number = -1;
}

The reason for this is that the == operator compares references ; that is it will return true if and only if the instance stored in variable speech is the same instance as the literal String you've created between double quotes ( "Hi" , "Thanks" , or "Bye" ).

Note also that I use the equalsIgnoreCase() call on the literal String I'm declaring, rather than the variable that is assigned from the parameter. This way, if a speech == null , the method call is still valid ( "Hi" will always be a String ), and so you won't get a NullPointerException , and the flow will continue until the else branch.

Answer 3

Try the following snippet:

Main.java

public class Main {
    public static void main(String[] args) {
        List<StringWithValue> stringList = new ArrayList<StringWithValue>();
        stringList.add(new StringWithValue("Hi", 1));
        stringList.add(new StringWithValue("Thanks", 2));
        stringList.add(new StringWithValue("Bye", 3));

        String speech = "Hi";
        int number = 0;

        for(StringWithValue swv : stringList){
            if(swv.getString().equals(speech)){
                number = swv.getValue();
                break;
            } else {
                number = -1;
        }

        System.out.println("The number for the speech is : " + number);
    }
}

StringWithValue.java

public class StringWithValue {
    private String string;
    private int value;

    public StringWithValue(String string, int value) {
        this.string = string;
        this.value = value;
    }

    public String getString() {
        return string;
    }

    public int getValue() {
        return value;
    }
}

Answer 4

public static double number;

    if(speech=="hi")
    {
        number=1;
    }
    else if(speech=="thanks")
    {
        number=2;
    }
    else if(speech=="Bye")
    {
        number=0;
    }
    else
    {
        System.out.println("Word Not Found");
    }