常用的java开发技巧总结

@Data
@Builder
public class CustomBodyDTO {
    private String name;
    private String idCode;
    private String status;
}
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public class TokenFactory {
    public TokenDTO buildToken(LoginInfo loginInfo) {
        String token = UUID.randomUUID().toString();
        TokenDTO tokenDTO = TokenDTO.builder()
                .token(token)
                .createTime(LocalDateTime.now())
                .build();
        String redisKey = RedisKeyBuilder.buildTokenKey(token);
        redisService.setObject(redisKey, loginInfo, Timeout.ONE_DAY * 30 * 2);
        log.info("创建token成功|loginInfo={}", loginInfo.toString());
        return tokenDTO;
    }
}
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public boolean equals(Object obj) {
        return (this == obj);
    }
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正确：“test”.equals(object);
错误：object.equals(“test”);
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private static class IntegerCache {
        static final int low = -128;
        static final int high;
        static final Integer cache[];
        static {
            // high value may be configured by property
            int h = 127;
            String integerCacheHighPropValue =
                sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
            if (integerCacheHighPropValue != null) {
                try {
                    int i = parseInt(integerCacheHighPropValue);
                    i = Math.max(i, 127);
                    // Maximum array size is Integer.MAX_VALUE
                    h = Math.min(i, Integer.MAX_VALUE - (-low) -1);
                } catch( NumberFormatException nfe) {
                    // If the property cannot be parsed into an int, ignore it.
                }
            }
            high = h;
            cache = new Integer[(high - low) + 1];
            int j = low;
            for(int k = 0; k < cache.length; k++)
                cache[k] = new Integer(j++);
            // range [-128, 127] must be interned (JLS7 5.1.7)
            assert IntegerCache.high >= 127;
        }
        private IntegerCache() {}
    }
  public static Integer valueOf(int i) {
        if (i >= IntegerCache.low && i <= IntegerCache.high)
            return IntegerCache.cache[i + (-IntegerCache.low)];
        return new Integer(i);
    }
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正确做法：
public class User {
    private Integer id;
    private String username;
    public Integer getId() {
        return id;
    }
    public User setId(Integer id) {
        this.id = id;
        return this;
    }
    public String getUsername() {
        return username;
    }
    public User setUsername(String username) {
        this.username = username;
        return this;
    }
}
错误做法：
public class User {
    private Integer id;
    private String username;
    public Integer getId() {
        return id;
    }
    public User setId(Integer id) {
        this.id = id;
        return this;
    }
    public String getUsername() {
        return "key-prefix-"+username;
    }
    public User setUsername(String username) {
        this.username = "key-prefix-"+username;
        return this;
    }
}
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Iterator<String> iterator = list.iterator();
while (iterator.hasNext()) {
String item = iterator.next();
if (删除元素的条件) {
iterator.remove();
}
}
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HashMap hashMap=new HashMap<>(13334);
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public boolean add(E e) {
        return map.put(e, PRESENT)==null;
    }
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ExecutorService executors = Executors.newSingleThreadExecutor();
      ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(5);
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ExecutorService fixedExecutorService = new ThreadPoolExecutor(
                1,
                2, 
                60,
                TimeUnit.SECONDS,
                 linkedBlockingQueue, 
                new MyThreadFactory(),
                new ThreadPoolExecutor.AbortPolicy()
        );
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正确做法：
        try {
            for (int i = 0; i < 100; i++) {
                doSomeThing();
            }
        }catch (Exception e){
            e.printStackTrace();
        }
不推荐做法：
       for (int i = 0; i < 100; i++) {
            try {
                doSomeThing();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
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File file = new File("*****");
        try (FileInputStream fin = new FileInputStream(file)) {
            //执行相关操作
        } catch (Exception e) {
            //异常捕获操作
        }
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private void grow(int minCapacity) {
        // overflow-conscious code
        int oldCapacity = elementData.length;
        int newCapacity = oldCapacity + (oldCapacity >> 1);
        if (newCapacity - minCapacity < 0)
            newCapacity = minCapacity;
        if (newCapacity - MAX_ARRAY_SIZE > 0)
            newCapacity = hugeCapacity(minCapacity);
        // minCapacity is usually close to size, so this is a win:
        elementData = Arrays.copyOf(elementData, newCapacity);
    }
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