局部变量，实例字段，输入参数和类字段之间有什么区别？ [英] What is the difference between a local variable, an instance field, an input parameter, and a class field?

问题描述

关于简单Java程序的局部变量，实例字段，输入参数和类字段有什么区别？

What is the difference between a local variable, an instance field, an input parameter, and a class field with respect to a simple Java program?

推荐答案

局部变量是在块的范围内定义的。它不能在该区块之外使用。

A local variable is defined within the scope of a block. It cannot be used outside of that block.

示例：

if(x > 10) {
    String local = "Local value";
}

我不能使用本地 之外阻止。

实例字段或 field ，是一个绑定到对象本身的变量。我可以在对象中使用它而无需使用访问器，对象中包含的任何方法都可以使用它。

An instance field, or field, is a variable that's bound to the object itself. I can use it in the object without the need to use accessors, and any method contained within the object may use it.

如果我想在外面使用它对象的，它不是 public ，我必须使用getter和/或setter。

If I wanted to use it outside of the object, and it was not public, I would have to use getters and/or setters.

示例：

public class Point {
    private int xValue; // xValue is a field

    public void showX() {
        System.out.println("X is: " + xValue);
    }
}

输入参数，或参数，甚至参数，是我们传递给方法或构造函数的东西。它具有关于我们传递给它的方法或构造函数的范围。

An input parameter, or parameter or even argument, is something that we pass into a method or constructor. It has scope with respect to the method or constructor that we pass it into.

示例：

public class Point {
    private int xValue;
    public Point(int x) {
        xValue = x;
   }

    public void setX(int x) {
        xValue = x;
    }
}

两者 x 参数绑定到不同的范围。

Both x parameters are bound to different scopes.

类字段或静态字段类似到一个字段，但区别在于你不需要有一个包含对象的实例来使用它。

A class field, or static field, is similar to a field, but the difference is that you do not need to have an instance of the containing object to use it.

示例：

System.out.println(Integer.MAX_VALUE);

我不需要整数检索所有整数的全局已知最大值。

I don't need an instance of Integer to retrieve the globally known maximum value of all ints.

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