On the failure of synchronized Lock

topic description

I use synchronized to lock the loop statement. It can be locked if the number of loops is less than 400. if it is more than 400, it cannot be locked. what is the reason for this?

related codes

    private void createThread(){
        thread1=new Thread1();
        thread2=new Thread1();
        thread1.start();
        thread2.start();
    }

    class Thread1 extends Thread{
        @Override
        public synchronized void run() {
            super.run();
            for(int i=0;i<500;iPP){
                MainTool.log(Thread.currentThread().getName()+":"+i);
            }
        }
    }

error display

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Thread-1:57
Thread-1:58
Thread-1:59
Thread-1:60
Thread-1:61
Thread-1:62
Thread-1:63
Thread-1:64
Thread-1:65
Thread-1:66
Thread-1:67
Thread-1:68
Thread-1:69
Thread-1:70
Thread-1:71
Thread-1:72
Thread-1:73
Thread-1:74
Thread-1:75
Thread-1:76
Thread-1:77
Thread-1:78
Thread-1:79
Thread-1:80
Thread-1:81
Thread-1:82
Thread-1:83
Thread-1:84
Thread-1:85
Thread-1:86
Thread-1:87
Thread-1:88
Thread-1:89
Thread-1:90
Thread-1:91
Thread-1:92
Thread-1:93
Thread-1:94
Thread-1:95
Thread-1:96
Thread-1:97
Thread-1:98
Thread-1:99
Thread-0:72
Thread-0:73
Thread-0:74
Thread-0:75
Thread-0:76
Thread-0:77
Thread-0:78
Thread-0:79
Thread-0:80
Thread-0:81
Thread-0:82
Thread-0:83
Thread-0:84
Thread-0:85
Thread-0:86
Thread-0:87
Thread-0:88
Thread-0:89
Thread-0:90
Thread-0:91
Thread-0:92
Thread-0:93
Thread-0:94
Thread-0:95
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Thread-0:107
Thread-0:108
Thread-0:109
Thread-0:110
Thread-0:111
Thread-0:112
Thread-0:113
Thread-0:123
Thread-1:109
Thread-0:124
Thread-1:110
Thread-0:125
Thread-1:111
Thread-0:126
Thread-1:112
Thread-0:127
Thread-1:113
Thread-0:128
Thread-0:136
Thread-0:137
Thread-0:138
Thread-0:139
Thread-0:140
Thread-0:141
Thread-0:142
Thread-0:143
Thread-0:144
Thread-1:114
Thread-0:178
Thread-1:121
Thread-0:186
Thread-1:122
Thread-0:187
Thread-1:123
Thread-0:188
Thread-1:124
Thread-1:125
Thread-1:126
Thread-1:127
Thread-1:128
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Thread-1:136
Thread-1:137
Thread-1:138
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Thread-1:140
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Thread-1:174
Thread-1:175
Thread-1:176
Thread-1:177
Thread-1:178
Thread-1:179
Thread-1:180
Thread-1:181
Thread-0:189
Thread-1:182
Thread-1:183
Thread-1:184
Thread-1:185
Thread-1:186
Thread-0:190
Thread-1:187
Thread-0:191
Thread-1:188
Thread-0:192
Thread-1:189
Thread-0:193
Thread-1:190
Thread-0:194
Thread-1:191
Thread-0:195
Thread-1:192
Thread-0:196
Thread-1:193
Thread-0:197
Thread-1:194
Thread-0:198
Thread-1:195
Thread-0:199
Thread-1:196
Thread-0:200
Thread-1:197
Thread-0:201
Thread-1:198
Thread-0:202
Thread-1:199
Thread-0:203
Thread-1:200
Thread-0:204
Thread-1:201
Thread-0:205
Thread-1:202
Thread-0:206
Thread-1:203
Thread-0:207
Thread-1:204
Thread-0:208
.....
Dec.29,2021

I don't see any errors in the results. Where do you think there are errors in the output?

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