为什么最终的字段变量不能分配给空白的Java？ [英] Why final field variable can not assign to blank in Java?

问题描述

与其他变量一样，我想将final字段类型变量分配给空白，但是初始化被Java阻止。它的逻辑是什么？也许我想使用我的变量的默认值？对于int = 0，string = null boolean = false等...

  public class Hello { 
 
 static final int myNumber; / *它提供空白的最终字段myNumber 
可能没有被初始化错误在Eclipse * / 
} 
  

解决方案

最终变量只能通过初始化器或赋值语句进行初始化一次。它不需要在声明点被初始化：这被称为空白最终变量。

更改代码

  public class Hello {
 
 final int myNumber; 
 public Hello（int num）{
 this.myNumber = num; 
} 
 
} 
  

静态最终变量使用静态块初始化

  static {
 myNumber = 0; 
} 
  

Like other variables, i want to assign final field type variable to blank but initialization is blocking by Java. What is the its logic? Maybe i want to use default values of my variables? for int = 0, string = null boolean = false etc...

public class Hello {

static final int myNumber; /* it is giving "The blank final field myNumber 
                                may not have been initialized" error in Eclipse */
}

解决方案

A final variable can only be initialized once, either via an initializer or an assignment statement. It does not need to be initialized at the point of declaration: this is called a "blank final" variable.

change your code

public class Hello {

final int myNumber; 
 public Hello(int num){
 this.myNumber = num;
}

}

for static final variable use static block for initialization

static{
        myNumber = 0;
    }

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