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Lookup Java enum by string value 23 answers

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您需要将String arg从命令行转换为枚举值。

Child c = Child.valueOf(args[0]);

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Use Enum.valueOf() . It takes an enum class and string as as argument and tries and find an enum by that name.

Note: throws IllegalArgumentException if not found... You'll have to catch it explicitly since this is an unchecked exception.

Another solution is to use .valueOf() on your enum class itself ( MyEnum.valueOf("whatever") ). Same warning as to exception handling applies.

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Your solution:

public enum Child {

    David(23),
    Johnson(34),
    Brackley(19);

    private int age;

    private Child(int age) {
        this.age=age; 
    }

    int getAge(){
        return age;
    }

    public static Child getAgeFromName(String name) {
        for(Child child : Child.values()) {
            if(child.toString().equalsIgnoreCase(name)) {
                return child;
            }
        }
        return null;
    }

    public static void main(String[] args) {
        if(args.length != 0) {
            Child child = Child.getAgeFromName(args[0]);
            if(child != null) {
                System.out.println(args[0] + " age is " + child.getAge());
            }else {
                System.out.println("No child exists with name " + args[0]);
            }
        } else {
            System.out.println("please provide a child name");
        }


    }
}

INPUT : OUTPUT
java Child David : David age is 23
java Child sam : No child exist with name sam
java Child : Please provide a child name

Hope this solves your problem

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