Java 根据输入字符串值返回类变量

我想创建一个接受字符串参数并返回该类型类的方法

例如，如果我通过

Long

，它应该返回

Long.class

psudo代码：

private Class<?> classReturn(String className){
return new Class<className>;
}

value = (classReturn(type)) value ;

---

关于编辑，不能将字符串值“强制转换”为长值。为了将字符串值转换为其他类型，您需要更复杂的东西，例如。

您正在查找

Class.forName（）

。但是，您需要类的完全限定名以及包。

您可以使用

Class.forName(className);

如果要使用较短的类名，则需要实现如下路径

转换字符串最接近的方法是采用某种约定，例如valueOf或接受字符串的构造函数

public static <T> T parseAs(String text, String className) {
    Class clazz;
    FOUND:
    {
        ClassNotFoundException e = null;
        for (String pkg : "java.lang.,java.util.,java.math.,".split(",",-1)) {
            try {
                clazz = Class.forName(pkg + className);
                break FOUND;
            } catch (ClassNotFoundException e2) {
                e = e2;
            }
        }
        throw new IllegalArgumentException(e);
    }
    try {
        Method valueOf = clazz.getMethod("valueOf", String.class);
        return (T) valueOf.invoke(null, text);
    } catch (Exception e) {
        try {
            Constructor<T> valueOf = clazz.getConstructor(String.class);
            return (T) valueOf.newInstance(text);
        } catch (Exception e2) {
            throw new IllegalArgumentException(e);
        }
    }
}

enum BuySell {
    BUY, SELL
}
public static void main(String... args) {
    for (String className : "String,Long,Double,BigDecimal".split(",")) {
        Object o = parseAs("1", className);
        System.out.println(className + " => " + o.getClass() + " as " + o);
    }
    Object o = parseAs("BUY", BuySell.class.getName());
    System.out.println("BuySell => " + o.getClass() + " as " + o);
}

---

我认为从上下文类加载器加载比Class.forName（）更好。它能保持永久性clean@Chris如果您使用自定义类和多个类装入器，这是一个好主意。那么Character类呢？它没有valueOf（字符串）；对于其他类，您需要编写一个适合您需要的自定义转换。

public static <T> T parseAs(String text, String className) {
    Class clazz;
    FOUND:
    {
        ClassNotFoundException e = null;
        for (String pkg : "java.lang.,java.util.,java.math.,".split(",",-1)) {
            try {
                clazz = Class.forName(pkg + className);
                break FOUND;
            } catch (ClassNotFoundException e2) {
                e = e2;
            }
        }
        throw new IllegalArgumentException(e);
    }
    try {
        Method valueOf = clazz.getMethod("valueOf", String.class);
        return (T) valueOf.invoke(null, text);
    } catch (Exception e) {
        try {
            Constructor<T> valueOf = clazz.getConstructor(String.class);
            return (T) valueOf.newInstance(text);
        } catch (Exception e2) {
            throw new IllegalArgumentException(e);
        }
    }
}

enum BuySell {
    BUY, SELL
}
public static void main(String... args) {
    for (String className : "String,Long,Double,BigDecimal".split(",")) {
        Object o = parseAs("1", className);
        System.out.println(className + " => " + o.getClass() + " as " + o);
    }
    Object o = parseAs("BUY", BuySell.class.getName());
    System.out.println("BuySell => " + o.getClass() + " as " + o);
}

String => class java.lang.String as 1
Long => class java.lang.Long as 1
Double => class java.lang.Double as 1.0
BigDecimal => class java.math.BigDecimal as 1
BuySell => class Main$BuySell as BUY