Master the 'Contracts for Java' framework in the java class library: from entry to proficiency
Master the 'Contracts for Java' framework in the java class library: from entry to proficiency
The 'Contracts for Java' in the Java Class Library is a powerful framework to achieve contract programming in the code.
What is contract programming?
Contract programming is a programming method based on front conditions, rear conditions and unchanged.It clearly defines and verify these conditions and invariance in the code to ensure the correctness and robustness of the program.
The basic principle of 'Contracts for Java' framework is to better understand and maintain the code by clearing the front conditions, rear conditions, and invariance of the code.
1. Pre -conditions
The front conditions refer to the conditions that need to be met before the method execution.By using the 'Contracts for Java' framework, we can use an assertion in the method to specify the front conditions and verify it during runtime.For example:
public int divide(int dividend, int divisor) {
Contract.requires(divisor != 0, "Divisor cannot be zero.");
return dividend / divisor;
}
In the above example, we used the method of `Contract.Requires ()` to specify the front conditions.If the division is zero, the assertion will trigger and throw an exception.
Second, rear conditions
The rear conditions refer to the conditions that should be met after the method execution.Using the 'Contracts for Java' framework, we can use an assertion in the method to specify the rear conditions and verify it.For example:
public int sum(int a, int b) {
int result = a + b;
Contract.ensures(result > a && result > b, "Sum should be greater than operands.");
return result;
}
In the above example, we use the method of `Contract.ensures () to specify the rear conditions.If the result is not met, assertions will trigger and throw an exception.
Three, unable style
Unable variable is a condition that should always remain unchanged during the implementation of the method.The 'Contracts for Java' framework specifies the unchanging formula by using an assertion in the code and verified during runtime.For example:
public class Circle {
private double radius;
public Circle(double radius) {
Contract.requires(radius > 0, "Radius must be positive.");
this.radius = radius;
}
public double getArea() {
Contract.invariant(radius > 0, "Radius must be positive.");
return Math.PI * radius * radius;
}
}
In the above example, we used the method of `Contract.Requires ()` to specify an unchanged formula in the constructor.At the same time, in the `Getarea ()` method, we used the `Contract.invariant ()` to verify whether the unable format is satisfied.If the conditions are not met, an assertion will trigger and throw an exception.
Summarize:
'Contracts for Java' framework is a powerful tool that helps us to achieve contract programming.By clearing and verifying the front conditions, rear conditions and unchanged formulas, we can improve the readability, maintenance and robustness of the code.Mastering this framework allows us to design and achieve high -quality Java programs.
