如果在init中使用了成员变量，那么成员变量一定要定义在init之前，否则会爆Variable cannot be initialized before declaration 错误

不管调用哪个次级构造函数，都是先执行主构造函数(初始化成员变量和执行init代码块)，再执行次级构造函数代码。所以kotlin规定次级构造函数先要委托给主构造函数。

成员变量初始化和init代码块谁先执行是按它们的声明顺序来的。

class InitTest {

    private var num1 = 2

    init {
        num1 = 3
        println("init方法:$num1")
    }

    init {
//        num2 = 5
        println("init方法2")
    }

    constructor() {
        println("构造函数1")
    }

    constructor(params: String) {
        println("构造函数2")
    }

    private var num2 = 4

}

public final class InitTest {
   private int num1;
   private int num2;

   public InitTest() {
      this.num1 = 2;
      this.num1 = 3;
      String var1 = "init方法:" + this.num1;
      System.out.println(var1);
      var1 = "init方法2";
      System.out.println(var1);
      this.num2 = 4;
      var1 = "构造函数1";
      System.out.println(var1);
   }

   public InitTest(@NotNull String params) {
      Intrinsics.checkNotNullParameter(params, "params");
      super();
      this.num1 = 2;
      this.num1 = 3;
      String var2 = "init方法:" + this.num1;
      System.out.println(var2);
      var2 = "init方法2";
      System.out.println(var2);
      this.num2 = 4;
      var2 = "构造函数2";
      System.out.println(var2);
   }
}
// InitTestKt.java
package com.lcf.study;

import kotlin.Metadata;

@Metadata(
   mv = {1, 9, 0},
   k = 2,
   d1 = {"\u0000\b\n\u0000\n\u0002\u0010\u0002\n\u0000\u001a\u0006\u0010\u0000\u001a\u00020\u0001¨\u0006\u0002"},
   d2 = {"main", "", "leetCodeJava"}
)
public final class InitTestKt {
   public static final void main() {
      new InitTest("222222222");
   }

   // $FF: synthetic method
   public static void main(String[] var0) {
      main();
   }
}