if(condition){
public static final test = "some value";
}

public class Test {

    public static final String test;
    static {
      String tmp = null;
        if (condition) {
            tmp = "ss";
        }
        test = tmp;
    }

}

public static final String test = condition ? "value" : "other value";

public enum Const {
    SAMPLE_1(10), SAMPLE_2(10, 20);

    private int value1, value2;
    private Const(int value1, int value2) {
        this.value1 = value1;
        this.value2 = value2;
    }

    private Const(int value1) {
        this.value1 = value1;
    }

    //Value based on condition
    public int getValue(boolean condition) {
        return condition == true ? value2 : value1;
    }

    //value which is not based on conditions
    public int getValue() {
        return value1;
    }
}

public interface InitializeInInterface {

    public static final String test = Initializer.init();

    static class Initializer {
        public static String init() {
            String result = "default value";
            InputStream is = InitializeInInterface.class.getClassLoader().getResourceAsStream("config.properties");
            Properties properties = new Properties();
            try {
                properties.load(is);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if ("bar".equals(properties.getProperty("foo"))) {
                result = "some value";
            }
            return result;
        }
    }
}