如果在init中使用了成員變量，那么成員變量一定要定義在init之前，否則會(huì)爆Variable cannot be initialized before declaration 錯(cuò)誤

不管調(diào)用哪個(gè)次級(jí)構(gòu)造函數(shù)，都是先執(zhí)行主構(gòu)造函數(shù)(初始化成員變量和執(zhí)行init代碼塊)，再執(zhí)行次級(jí)構(gòu)造函數(shù)代碼。所以kotlin規(guī)定次級(jí)構(gòu)造函數(shù)先要委托給主構(gòu)造函數(shù)。

成員變量初始化和init代碼塊誰(shuí)先執(zhí)行是按它們的聲明順序來(lái)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("構(gòu)造函數(shù)1")
    }

    constructor(params: String) {
        println("構(gòu)造函數(shù)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 = "構(gòu)造函數(shù)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 = "構(gòu)造函數(shù)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();
   }
}