Java code block example analysis

1. Ordinary code blocks

Ordinary code blocks refer to code blocks that are defined directly in methods or statements

public class CodeDemo {

public static void main(String[] args) {

// 普通代码块
               {
int x = 10; // 局部变量
System.out.println("普通代码块---》"+x);  //10
}
int x = 100;
System.out.println("代码块之外---》"+x);  //100
}
}

2. Construction code block

public class CodeBlock
{
    {
        System.out.println("构造代码块");
    }

    CodeBlock(){
        System.out.println("构造方法");
    }
}

public class Test
{
    public static void main(String[] args) {
        CodeBlock codeBlock = new CodeBlock();

    }
}

//执行结果
//构造代码块
//构造方法

3. Static code block

Appears outside the method in the class and adds static modification, often used to initialize a class, is executed when loading, and the static code block is executed once.

public class CodeBlock
{
    {
        System.out.println("静态代码块");
    }

    {
        System.out.println("构造代码块");
    }

    CodeBlock(){
        System.out.println("构造方法");
    }
}

public class Test
{
    public static void main(String[] args) {
        CodeBlock codeBlock = new CodeBlock();
    }
}

//执行结果
//静态代码块
//构造代码块
//构造方法

4. Local code block

Scope: exists in the method

public static void main (String[] args){
    {
        int number = 1;
    }
    System.out.println(number);//异常
}

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