if else语句中的Android字符串值

String userInput = "hello";

if (userInput.equals("hello")) {
    // 执行当用户输入为"hello"时的操作
    System.out.println("Hello, user!");
} else if (userInput.equals("goodbye")) {
    // 执行当用户输入为"goodbye"时的操作
    System.out.println("Goodbye, user!");
} else {
    // 执行当用户输入既不是"hello"也不是"goodbye"时的操作
    System.out.println("I don't understand that input.");
}

String str1 = "hello";
String str2 = new String("hello");

// 错误的比较方式
if (str1 == str2) {
    System.out.println("Strings are equal.");
} else {
    System.out.println("Strings are not equal.");
}

// 正确的比较方式
if (str1.equals(str2)) {
    System.out.println("Strings are equal.");
} else {
    System.out.println("Strings are not equal.");
}

String userInput = "";

if (userInput != null && userInput.equals("hello")) {
    System.out.println("Hello, user!");
} else {
    System.out.println("I don't understand that input.");
}