关于类：为什么不是Java中的一切都是静态函数？以下两个例子有什么不同吗？

Why not everything is static function in java? Any differences in following two examples?

本问题已经有最佳答案，请猛点这里访问。

假设您有以下两个类，第一个是长方体类，第二个是描述操作的类。

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public class Cuboid {
private double length;
private double width;
private double height;

public Cuboid(double length, double width, double height) {
super();
this.length = length;
this.width = width;
this.height = height;
}

public double getVolume() {
return length * width * height;
}

public double getSurfaceArea() {
return 2 * (length * width + length * height + width * height);
}
}

为什么不使用抽象类：

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public class Cuboid {
public static double getVolume(double length, double width, double height) {
return length * width * height;
}

public static double getSurfaceArea(double length, double width, double height) {
return 2 * (length * width + length * height + width * height);
}
}

因此，如果您想获得一个盒子的体积，只需使用以下代码：

1	double boxVolume = Cuboid.getVolume(2.0, 1.0,3.0);

下面的例子如何使用AWS Java SDK呢？

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public class CreateVolumeBuilder {
private AmazonEC2 ec2;
private int size;
private String availabilityZone;

public CreateVolumeBuilder(AmazonEC2 ec2, int size, String availabilityZone) {
super();
this.ec2 = ec2;
this.size = size;
this.availabilityZone = availabilityZone;
}

public static CreateVolumeResult getVolume() {
CreateVolumeResult createVolumeResult = ec2
.createVolume(new CreateVolumeRequest().withAvailabilityZone(availabilityZone).withSize(size));
return createVolumeResult;
}
}

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public class CreateVolumeBuilder {
public static CreateVolumeResult getVolume(AmazonEC2 ec2, int size, String availabilityZone) {
CreateVolumeResult createVolumeResult= ec2.createVolume(new CreateVolumeRequest().withAvailabilityZone(availabilityZone).withSize(size));
return createVolumeResult;
}
}