如何在 if 条件的末尾 Return 数组列表的对象？

Question

我有一个数组列表，它需要在末尾 return allteams 对象，但我无法做到这一点，当传递 null 时，它给出了一个空指针异常，请帮助我解决这个问题。这是代码示例：

private ArrayList<Team> getData() {
    Intent localIntent = getIntent();
    localIntent.getIntExtra("det", 0);
    if (localIntent.hasExtra("beg")) {


        Team t1 = new Team("Day 1: Chest, Back, Shoulders, Legs, Biceps, Triceps");
        t1.players.add("Chest – Barbell Bench Press – 4 sets of 8 reps");
        t1.players.add("Back – Lat-pulldowns – 4 sets of 10 reps");
        t1.players.add("Shoulders – Seated Dumbbell Press – 4 sets of 10 reps");
        t1.players.add("Legs – Leg Extensions – 4 sets of 10 reps");
        t1.players.add("Biceps – Barbell Bbicep Curls – 3 sets of 10 reps");
        t1.players.add("Triceps – Triceps Rope Pushdowns – 3 sets of 15 reps");

        Team t2 = new Team("Day 2: Legs, Triceps, Biceps, Chest, Back, Shoulder");
        t2.players.add("Legs – Leg Press Machine – 4 sets of 8 reps");
        t2.players.add("Triceps – Overhead Bar Extensions – 3 sets of 20 reps");
        t2.players.add("Biceps – EZ Bar Curls – 4 sets of 10 reps");
        t2.players.add("Chest – Machine Chest Press – 4 sets of 10 reps");
        t2.players.add("Back – T-Bar Row – 4 sets of 10 reps");
        t2.players.add("Shoulders – Lateral Raises – 3 sets of 20 reps");

        Team t3 = new Team("Day 3: Shoulders, Back, Chest, Legs, Triceps, Biceps");
        t3.players.add("Shoulders – Upright Rows – 3 sets of 15 reps");
        t3.players.add("Back – Close-Grip Pulldowns – 4 sets of 12 reps");
        t3.players.add("Chest – Fly – 4 sets of 10 reps");
        t3.players.add("Legs – Lunges – 3 sets of 10 reps per leg");
        t3.players.add("Triceps – Skullcrushers – 3 sets of 15 reps");
        t3.players.add("Biceps – Hammer Curls – 3 sets of 12 reps");

        ArrayList<Team> allTeams = new ArrayList<Team>();
        allTeams.add(t1);
        allTeams.add(t2);
        allTeams.add(t3);

        return allTeams;


    } else if (localIntent.hasExtra("inter")) {

        Team t1 = new Team("Day 1: Chest, Shoulders and Triceps");
        t1.players.add("Bench Press – 3 sets of 10, 10, 8 (adding weight) reps");
        t1.players.add("Incline Dumbbell Bench Press – 3 sets of 10 reps");
        t1.players.add("Chest Dip – 3 sets of MAX reps");
        t1.players.add("Skullcrushers – 3 sets of 8-10 Reps");
        t1.players.add("One Arm Dumbbell Extension – 3 sets of 10 reps");
        t1.players.add("Tricep Extension – 3 sets of 10 reps");
        t1.players.add("Barbell Front Raise – 4 sets of 12 reps");
        t1.players.add("Dumbbell Lateral Raise – 4 sets of 15, 12, 8, 8 (adding weight) reps");

        Team t2 = new Team("Day 2: Back and Biceps");
        t2.players.add("Wide Grip Pull Up 3 sets of MAX reps");
        t2.players.add("Lat Pull Down – 3 sets of 10 reps");
        t2.players.add("Straight Arm Lat Pull Down – 3 sets of 10 reps");
        t2.players.add("Standing Barbell Curl – 3 sets of 8-10 reps");
        t2.players.add("Preacher Curl – 3 sets of 10 reps");
        t2.players.add("Incline Dumbbell Curl – 3 sets of 10 reps");


        Team t3 = new Team("Day 3: Legs");
        t3.players.add("Squat – 4 sets of 10,10,8,8 reps");
        t3.players.add("Dumbbell Lunge – 3 sets of 8 on each leg");
        t3.players.add("Leg Press – 3 sets of 12 reps");
        t3.players.add("Leg Curl – 3 sets of 15 reps");
        t3.players.add("Leg Extension – 3 sets of 15 reps");
        t3.players.add("Standing Calf Raise – 5 sets of 10,8,8,8,6 (heavy)reps");
        t3.players.add("Seated Calf Raise – 5 sets of 15 (light) reps");

        Team t4 = new Team("Day 4:  Shoulders, chest, and Triceps");
        t4.players.add("Barbell Bench Press – 3 sets of 10, 10, 8 reps");
        t4.players.add("Dumbbell Flys – 3 sets of 10 reps");
        t4.players.add("Cable Crossovers – 3 sets of 10 reps");
        t4.players.add("Close Grip Bench Press – 4 sets of 10, 10, 8, 6 reps");
        t4.players.add("Lying Dumbbell Extension – 3 sets of 10 reps");
        t4.players.add("Tricep Kickback – 3 sets of 10 reps");
        t4.players.add("Seated Dumbbell Press – 4 sets of 10, 10, 8, 8 reps");
        t4.players.add("One Arm Cable Lateral Raise – 3 sets of 12 reps");

        Team t5 = new Team("Day 5: Back and Biceps");
        t5.players.add("Seated Row – 4 sets of 10 reps");
        t5.players.add("Bent Over Barbell Row – 3 sets of 10 reps");
        t5.players.add("Bent Over Row – 3 sets of 12 reps");
        t5.players.add("Smith Machine Upright Row – 3 sets of 8-10 reps");
        t5.players.add("Cable Curl – 4 sets of 8-10 reps");
        t5.players.add("Concentration Curl – 3 sets of 10 reps");
        t5.players.add("Reverse Barbell Curl – 3 sets of 10 reps");

        ArrayList<Team> allTeams = new ArrayList<Team>();
        allTeams.add(t1);
        allTeams.add(t2);
        allTeams.add(t3);
        allTeams.add(t4);
        allTeams.add(t5);

        return allTeams;
    }
    return null;
}

请帮我解决这个问题我该怎么做才能在最后解决这个问题而不是 null 它应该是 returning allteams。

Answer 1

通过这些代码，如果不匹配任何东西，对于这些情况，它的 return null 添加最后一个 else 并设置它的默认值。无论它是否为 null 或不匹配，它都执行 else 语句。

if()
{
}
else if()
 {
 }
else  {
    Team t1 = new Team("Day 1: Chest, Shoulders and Triceps");
    t1.players.add("Bench Press – 3 sets of 10, 10, 8 (adding weight) reps");
    t1.players.add("Incline Dumbbell Bench Press – 3 sets of 10 reps");
    t1.players.add("Chest Dip – 3 sets of MAX reps");
    t1.players.add("Skullcrushers – 3 sets of 8-10 Reps");
    t1.players.add("One Arm Dumbbell Extension – 3 sets of 10 reps");
    t1.players.add("Tricep Extension – 3 sets of 10 reps");
    t1.players.add("Barbell Front Raise – 4 sets of 12 reps");
    t1.players.add("Dumbbell Lateral Raise – 4 sets of 15, 12, 8, 8 (adding weight) reps");
    ArrayList<Team> allTeams = new ArrayList<Team>();
    allTeams.add(t1);       
    return allTeams;
}

Answer 2

而你想要 return 一个数组，如果没有对应的条件？因为你最后是returning null，如果没有对应的，你可以试试这个。

private ArrayList<Team> getData() {
   Intent localIntent = getIntent();
   localIntent.getIntExtra("det", 0);
   ArrayList<Team> allTeams = new ArrayList<Team>();

   if (localIntent.hasExtra("beg")) {


    Team t1 = new Team("Day 1: Chest, Back, Shoulders, Legs, Biceps, Triceps");
    t1.players.add("Chest – Barbell Bench Press – 4 sets of 8 reps");
    t1.players.add("Back – Lat-pulldowns – 4 sets of 10 reps");
    t1.players.add("Shoulders – Seated Dumbbell Press – 4 sets of 10 reps");
    t1.players.add("Legs – Leg Extensions – 4 sets of 10 reps");
    t1.players.add("Biceps – Barbell Bbicep Curls – 3 sets of 10 reps");
    t1.players.add("Triceps – Triceps Rope Pushdowns – 3 sets of 15 reps");

    Team t2 = new Team("Day 2: Legs, Triceps, Biceps, Chest, Back, Shoulder");
    t2.players.add("Legs – Leg Press Machine – 4 sets of 8 reps");
    t2.players.add("Triceps – Overhead Bar Extensions – 3 sets of 20 reps");
    t2.players.add("Biceps – EZ Bar Curls – 4 sets of 10 reps");
    t2.players.add("Chest – Machine Chest Press – 4 sets of 10 reps");
    t2.players.add("Back – T-Bar Row – 4 sets of 10 reps");
    t2.players.add("Shoulders – Lateral Raises – 3 sets of 20 reps");

    Team t3 = new Team("Day 3: Shoulders, Back, Chest, Legs, Triceps, Biceps");
    t3.players.add("Shoulders – Upright Rows – 3 sets of 15 reps");
    t3.players.add("Back – Close-Grip Pulldowns – 4 sets of 12 reps");
    t3.players.add("Chest – Fly – 4 sets of 10 reps");
    t3.players.add("Legs – Lunges – 3 sets of 10 reps per leg");
    t3.players.add("Triceps – Skullcrushers – 3 sets of 15 reps");
    t3.players.add("Biceps – Hammer Curls – 3 sets of 12 reps");

    allTeams.add(t1);
    allTeams.add(t2);
    allTeams.add(t3);

    return allTeams;


} else if (localIntent.hasExtra("inter")) {

    Team t1 = new Team("Day 1: Chest, Shoulders and Triceps");
    t1.players.add("Bench Press – 3 sets of 10, 10, 8 (adding weight) reps");
    t1.players.add("Incline Dumbbell Bench Press – 3 sets of 10 reps");
    t1.players.add("Chest Dip – 3 sets of MAX reps");
    t1.players.add("Skullcrushers – 3 sets of 8-10 Reps");
    t1.players.add("One Arm Dumbbell Extension – 3 sets of 10 reps");
    t1.players.add("Tricep Extension – 3 sets of 10 reps");
    t1.players.add("Barbell Front Raise – 4 sets of 12 reps");
    t1.players.add("Dumbbell Lateral Raise – 4 sets of 15, 12, 8, 8 (adding weight) reps");

    Team t2 = new Team("Day 2: Back and Biceps");
    t2.players.add("Wide Grip Pull Up 3 sets of MAX reps");
    t2.players.add("Lat Pull Down – 3 sets of 10 reps");
    t2.players.add("Straight Arm Lat Pull Down – 3 sets of 10 reps");
    t2.players.add("Standing Barbell Curl – 3 sets of 8-10 reps");
    t2.players.add("Preacher Curl – 3 sets of 10 reps");
    t2.players.add("Incline Dumbbell Curl – 3 sets of 10 reps");


    Team t3 = new Team("Day 3: Legs");
    t3.players.add("Squat – 4 sets of 10,10,8,8 reps");
    t3.players.add("Dumbbell Lunge – 3 sets of 8 on each leg");
    t3.players.add("Leg Press – 3 sets of 12 reps");
    t3.players.add("Leg Curl – 3 sets of 15 reps");
    t3.players.add("Leg Extension – 3 sets of 15 reps");
    t3.players.add("Standing Calf Raise – 5 sets of 10,8,8,8,6 (heavy)reps");
    t3.players.add("Seated Calf Raise – 5 sets of 15 (light) reps");

    Team t4 = new Team("Day 4:  Shoulders, chest, and Triceps");
    t4.players.add("Barbell Bench Press – 3 sets of 10, 10, 8 reps");
    t4.players.add("Dumbbell Flys – 3 sets of 10 reps");
    t4.players.add("Cable Crossovers – 3 sets of 10 reps");
    t4.players.add("Close Grip Bench Press – 4 sets of 10, 10, 8, 6 reps");
    t4.players.add("Lying Dumbbell Extension – 3 sets of 10 reps");
    t4.players.add("Tricep Kickback – 3 sets of 10 reps");
    t4.players.add("Seated Dumbbell Press – 4 sets of 10, 10, 8, 8 reps");
    t4.players.add("One Arm Cable Lateral Raise – 3 sets of 12 reps");

    Team t5 = new Team("Day 5: Back and Biceps");
    t5.players.add("Seated Row – 4 sets of 10 reps");
    t5.players.add("Bent Over Barbell Row – 3 sets of 10 reps");
    t5.players.add("Bent Over Row – 3 sets of 12 reps");
    t5.players.add("Smith Machine Upright Row – 3 sets of 8-10 reps");
    t5.players.add("Cable Curl – 4 sets of 8-10 reps");
    t5.players.add("Concentration Curl – 3 sets of 10 reps");
    t5.players.add("Reverse Barbell Curl – 3 sets of 10 reps");

    allTeams.add(t1);
    allTeams.add(t2);
    allTeams.add(t3);
    allTeams.add(t4);
    allTeams.add(t5);

    return allTeams;
    }
  return allTeams;
}

我已将 allTeams 数组放在方法的开头。你可以试试看是否有效。但是如果真的要return null 的时候没有条件。但是您需要检查 returning 中的 allTeams 是否不为空。

Answer 3

private ArrayList<Team> getData() {
Intent localIntent = getIntent();
localIntent.getIntExtra("det", 0);
ArrayList<Team> allTeams = new ArrayList<Team>();
if (localIntent.hasExtra("beg")) {


    Team t1 = new Team("Day 1: Chest, Back, Shoulders, Legs, Biceps, Triceps");
    t1.players.add("Chest – Barbell Bench Press – 4 sets of 8 reps");
    t1.players.add("Back – Lat-pulldowns – 4 sets of 10 reps");
    t1.players.add("Shoulders – Seated Dumbbell Press – 4 sets of 10 reps");
    t1.players.add("Legs – Leg Extensions – 4 sets of 10 reps");
    t1.players.add("Biceps – Barbell Bbicep Curls – 3 sets of 10 reps");
    t1.players.add("Triceps – Triceps Rope Pushdowns – 3 sets of 15 reps");

    Team t2 = new Team("Day 2: Legs, Triceps, Biceps, Chest, Back, Shoulder");
    t2.players.add("Legs – Leg Press Machine – 4 sets of 8 reps");
    t2.players.add("Triceps – Overhead Bar Extensions – 3 sets of 20 reps");
    t2.players.add("Biceps – EZ Bar Curls – 4 sets of 10 reps");
    t2.players.add("Chest – Machine Chest Press – 4 sets of 10 reps");
    t2.players.add("Back – T-Bar Row – 4 sets of 10 reps");
    t2.players.add("Shoulders – Lateral Raises – 3 sets of 20 reps");

    Team t3 = new Team("Day 3: Shoulders, Back, Chest, Legs, Triceps, Biceps");
    t3.players.add("Shoulders – Upright Rows – 3 sets of 15 reps");
    t3.players.add("Back – Close-Grip Pulldowns – 4 sets of 12 reps");
    t3.players.add("Chest – Fly – 4 sets of 10 reps");
    t3.players.add("Legs – Lunges – 3 sets of 10 reps per leg");
    t3.players.add("Triceps – Skullcrushers – 3 sets of 15 reps");
    t3.players.add("Biceps – Hammer Curls – 3 sets of 12 reps");

    allTeams.add(t1);
    allTeams.add(t2);
    allTeams.add(t3);


} else if (localIntent.hasExtra("inter")) {

    Team t1 = new Team("Day 1: Chest, Shoulders and Triceps");
    t1.players.add("Bench Press – 3 sets of 10, 10, 8 (adding weight) reps");
    t1.players.add("Incline Dumbbell Bench Press – 3 sets of 10 reps");
    t1.players.add("Chest Dip – 3 sets of MAX reps");
    t1.players.add("Skullcrushers – 3 sets of 8-10 Reps");
    t1.players.add("One Arm Dumbbell Extension – 3 sets of 10 reps");
    t1.players.add("Tricep Extension – 3 sets of 10 reps");
    t1.players.add("Barbell Front Raise – 4 sets of 12 reps");
    t1.players.add("Dumbbell Lateral Raise – 4 sets of 15, 12, 8, 8 (adding weight) reps");

    Team t2 = new Team("Day 2: Back and Biceps");
    t2.players.add("Wide Grip Pull Up 3 sets of MAX reps");
    t2.players.add("Lat Pull Down – 3 sets of 10 reps");
    t2.players.add("Straight Arm Lat Pull Down – 3 sets of 10 reps");
    t2.players.add("Standing Barbell Curl – 3 sets of 8-10 reps");
    t2.players.add("Preacher Curl – 3 sets of 10 reps");
    t2.players.add("Incline Dumbbell Curl – 3 sets of 10 reps");


    Team t3 = new Team("Day 3: Legs");
    t3.players.add("Squat – 4 sets of 10,10,8,8 reps");
    t3.players.add("Dumbbell Lunge – 3 sets of 8 on each leg");
    t3.players.add("Leg Press – 3 sets of 12 reps");
    t3.players.add("Leg Curl – 3 sets of 15 reps");
    t3.players.add("Leg Extension – 3 sets of 15 reps");
    t3.players.add("Standing Calf Raise – 5 sets of 10,8,8,8,6 (heavy)reps");
    t3.players.add("Seated Calf Raise – 5 sets of 15 (light) reps");

    Team t4 = new Team("Day 4:  Shoulders, chest, and Triceps");
    t4.players.add("Barbell Bench Press – 3 sets of 10, 10, 8 reps");
    t4.players.add("Dumbbell Flys – 3 sets of 10 reps");
    t4.players.add("Cable Crossovers – 3 sets of 10 reps");
    t4.players.add("Close Grip Bench Press – 4 sets of 10, 10, 8, 6 reps");
    t4.players.add("Lying Dumbbell Extension – 3 sets of 10 reps");
    t4.players.add("Tricep Kickback – 3 sets of 10 reps");
    t4.players.add("Seated Dumbbell Press – 4 sets of 10, 10, 8, 8 reps");
    t4.players.add("One Arm Cable Lateral Raise – 3 sets of 12 reps");

    Team t5 = new Team("Day 5: Back and Biceps");
    t5.players.add("Seated Row – 4 sets of 10 reps");
    t5.players.add("Bent Over Barbell Row – 3 sets of 10 reps");
    t5.players.add("Bent Over Row – 3 sets of 12 reps");
    t5.players.add("Smith Machine Upright Row – 3 sets of 8-10 reps");
    t5.players.add("Cable Curl – 4 sets of 8-10 reps");
    t5.players.add("Concentration Curl – 3 sets of 10 reps");
    t5.players.add("Reverse Barbell Curl – 3 sets of 10 reps");

    allTeams.add(t1);
    allTeams.add(t2);
    allTeams.add(t3);
    allTeams.add(t4);
    allTeams.add(t5);

}
return allTeams;
}

试试这个，无论你在哪里使用这个方法，在使用之前检查一下

ArrayList teamList = getData()
if(teamList.isNotEmpty()){
*do your stuff with teamList here*
}

如何在 if 条件的末尾 Return 数组列表的对象？

How To Return Object of Array List at the end of if condition?

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