The value of the local variable is not used

问题

all of the variables above have the warning in the title. Could you please tell me why that is happening?

public class DataTypes {
    public static void main(String[] argv) {
        // new feature in JDK 7
        int x = 0b1010; // 12
        int y = 0b1010_1010;
        int ssn = 444_12_7691;
        long phone = 408_777_6666L;
        double num = 9_632_401_909.1_0_3;
        String twoLine = "line one\nline two";
    }
}

回答1:

The variables you declared are never used, only assigned to, therefore you're being warned.

回答2:

You have defined the variables: x, y, ssn, phone, num and twoLine. But you never use the variables anywhere in the code. For instance, if you print the variables out:

System.out.println(x + y + ssn + phone + num + twoLine);

All the warnings should disappear

来源：https://stackoverflow.com/questions/36728961/the-value-of-the-local-variable-is-not-used