Java泛型编译失败

Question

public <T> void saveData(String key, T value) {

        SharedPreferences.Editor editor =  sharedPreferences.edit();

        if (value instanceof String) {
            editor.putString(key, (String) value);
        } else if (value instanceof Boolean) {
            editor.putBoolean(key, (boolean) value);
        } else if (value instanceof Integer) {
            editor.putInt(key, (int) value);
        } else if (value instanceof Float) {
            editor.putFloat(key, (float) value);
        } else if (value instanceof Long) {
            editor.putLong(key, (long) value);
        } else {
            System.out.println("Unknown type");
        }

        editor.apply();
    }

When I am building the project then I am getting error as

error: incompatible types: T cannot be converted to boolean
where T is a type-variable:
T extends Object declared in method <T>saveData(String,T)

This error is coming for long, int and float as well.

Answer 1

The error is only for primitive types, so pay attention on using primiteves instead of Objects. Generics work with objects.

Another way to achieve this with no if at all, so cyclomatic complexity 0:

blic void caller(){
    SharedPreferences.Editor editor = sharedPreferences.edit();
    saveDate(editor, "key-string", "string value");
    saveDate(editor, "key-boolean", true);
    saveDate(editor, "key-integer", 7);
    saveDate(editor, "key-float", 7.0f);
    saveDate(editor, "key-long", 7L);
    editor.apply();
}


public void saveData(Editor editor, String key, String value) {
    editor.putString(key, (String) value);
}

public void saveData(Editor editor, String key, Boolean value) {
    editor.putBoolean(key, (boolean) value);
}

public void saveData(Editor editor, String key, Integer value) {
    editor.putInt(key, (int) value);
}
public void saveData(Editor editor, String key, Float value) {
    editor.putFloat(key, (float) value);
}
public void saveData(Editor editor, String key, Long value) {
    editor.putLong(key, (long) value);
}

This way you pay the penalty in number of rows which is higher.