字符串valueOf与空字符串的串联

public void foo(){int intVar = 5;String strVar = intVar+"";    }

这种方法使用StringBuilder创建结果字符串

public void foo();  Code:   0:   iconst_5   1:   istore_1   2:   new     #2; //class java/lang/StringBuilder   5:   dup   6:   invokespecial   #3; //Method java/lang/StringBuilder."<init>":()V   9:   iload_1   10:  invokevirtual   #4; //Method java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder;   13:  ldc     #5; //String   15:  invokevirtual   #6; //Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;   18:  invokevirtual   #7; //Method java/lang/StringBuilder.toString:()Ljava/lang/String;   21:  astore_2   22:  return

public void bar(){int intVar = 5;String strVar = String.valueOf(intVar);}

此方法仅调用的静态方法

String

public void bar();  Code:   0:   iconst_5   1:   istore_1   2:   iload_1   3:   invokestatic    #8; //Method java/lang/String.valueOf:(I)Ljava/lang/String;   6:   astore_2   7:   return

依次调用

Integer.toString()